National Overview - December 2013
NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.
Maps and Graphics
Temperature and Precipitation Ranks
U.S. Percentage Areas
Supplemental December 2013 Information
- Year-to-date temperature evolution for select U.S. cities
- Year-to-date precipitation evolution for the contiguous U.S.
- 2013 U.S. Drought Improvement
- 2013 Alaska Extremes
- Select U.S. stations with extreme year
- Climate Highlights — December
- The average contiguous U.S. temperature for December was 30.9°F, 2.0°F below the 20th century average. This was the 21st coldest December on record for the nation and the coldest since 2009.
- Below-average temperatures were widespread across the West, the Plains States, and the Upper Midwest. Minnesota had its eighth coldest December on record with an average temperature of 5.8°F, 8.8°F below average. North Dakota tied its 9th coldest December with an average temperature of 4.5°F, 8.4°F below average.
- Above-average temperatures were observed across parts of the Southeast and Mid-Atlantic. Florida had its sixth warmest December with a statewide average temperature of 64.6°F, 5.0°F above average.
- The national precipitation total during December was 2.17 inches, 0.06 inch below the 20th century average, ranking near the median value in the 119-year period of record.
- Above-average precipitation was observed in the Northern Plains and Rockies, the Southeast, the Mid-Atlantic and the Midwest. Alabama, Georgia, North Dakota, Ohio, Virginia, and West Virginia, each had December precipitation totals that ranked among the ten wettest on record.
- Below-average precipitation was observed in the Central Plains and the West Coast. California had its second driest December on record, punctuating the driest calendar year on record for the state. Oregon had its third driest December, while Washington had its sixth driest.
- According to the December 31st U.S. Drought Monitor report, the national drought footprint changed little during the month with drought conditions impacting approximately 31.0 percent of the contiguous United States. Abnormally dry conditions expanded in the Northwest, and improved across the Southeast.
- Several snow storms impacted the Intermountain West, Northern Plains, Midwest and Northeast during December. According to the Rutgers Global Snow Lab, the December snow cover extent for the contiguous U.S. was 1.5 million square miles, which was 317,000 square miles above the 1981-2010 average. This ranked as the eighth largest December snow cover extent on record, and the largest since December 2009.
- Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand during December was 15 percent above average and the 41st highest in the 1895-2013 period of record.
**A comparison of the national temperature departure from average as calculated by NCDC's operational dataset (USHCN) and the U.S. Climate Reference Network (USCRN) is available on our National Temperature Index page.**
Alaska Temperature and Precipitation:
- Alaska had its 28ᵗʰ warmest December since records began in 1918, with a temperature 1.90°F (1.06°C) above the 1971-2000 average.
- Alaska had its 6ᵗʰ warmest October-December since records began in 1918, with a temperature 4.28°F (2.38°C) above the 1971-2000 average.
- Alaska had its 10ᵗʰ warmest January-December since records began in 1918, with a temperature 1.79°F (0.99°C) above the 1971-2000 average.
- Alaska had its 5ᵗʰ wettest December since records began in 1918, with an anomaly that was 51.00% above the 1971-2000 average.
- Alaska had its 2ⁿᵈ wettest October-December since records began in 1918, with an anomaly that was 52.86% above the 1971-2000 average.
- Alaska had its 3ʳᵈ wettest January-December since records began in 1918, with an anomaly that was 25.10% above the 1971-2000 average.
- Northeast Region: (Information provided by the Northeast Regional Climate Center)
- December was another cooler-than-average month in the Northeast. With an average temperature of 28.1 degrees F (-2.2 degrees C), it was 0.7 degrees F (0.4 degrees C) cooler than normal. Six states were cooler than normal, with departures ranging from -4.8 degrees F (-2.7 degrees C) in Maine to -0.4 degrees F (-0.2 degrees C) in Connecticut. Vermont ended the month at normal. Departures for the five warm states ranged from +0.3 degrees F (+0.2 degrees C) in Pennsylvania to +3.4 degrees F (+1.9 degrees C) in Delaware, making it their 16th warmest December on record. The year 2013 was slightly warmer-than-normal in the Northeast. The average temperature of 47.7 degrees F (8.7 degrees C) was 0.2 degrees F (0.1 degrees C) above average. Nine states were warmer than normal, with four of them ranking the year among their top 20 warmest. State departures ranged from -0.3 degrees F (-0.2 degrees C) in Maryland up to +1.0 degree F (+0.6 degrees C) in Vermont.
- The Northeast's three-month dry streak ended in December, as the region received 4.16 inches (105.66 mm) of precipitation, 119 percent of normal. The states were split, with six wetter than normal and six drier than normal. Of the six wet states, three ranked the month among their top 20 wettest and departures ranged from 104 percent of normal in Maine to 171 percent of normal in West Virginia (their 4th wettest December on record). For the dry states, departures ranged from 99 percent of normal in Massachusetts and Rhode Island to 95 percent of normal in Vermont. The Northeast ended 2013 slightly wetter than normal, receiving 44.87 inches (1139.70 mm) of precipitation for the year, 101 percent of normal. Seven states were wetter than normal, with one ranking the year among their top 20 wettest. Departures ranged from 87 percent of normal in Connecticut to 108 percent of normal in Delaware.
- According to the U.S. Drought Monitor, at the start of December, 35 percent of the Northeast was experiencing abnormally dry (D0) or moderate drought (D1) conditions. With several storms throughout the month, dryness eased slightly and by month's end 30 percent of the region was experiencing D0 or D1 conditions.
- Winter weather created travel problems throughout the month. Several large multi-vehicle accidents occurred including a 65-car pileup on Interstate 290 near Worcester, Massachusetts, on the 1st; a 50-car pileup on the Pennsylvania Turnpike on the 8th; a 30-car pileup on the Gowanus Expressway in Brooklyn, New York, on the 17th; and a 30-car pileup on the Pennsylvania Turnpike on the 26th. Flights were also affected, especially on the 8th when flight delays reached nearly 4.5 hours at the Philadelphia International Airport and a ground stop was issued at Reagan National Airport in Washington, D.C. From December 10-13, lake-effect snows of nearly five feet (1.5 m) accumulated in parts of New York. A snow total of 58.0 inches (147.3 cm) was reported in Redfield (east of Lake Ontario), while 44.0 inches (111.8 cm) was reported in Colden (east of Lake Erie). A pre-Christmas storm brought warm air and messy conditions to the region from December 21-22. On the 21st, twelve of the 35 first-order sites in the Northeast set high temperature records and on the 22nd, 25 sites set high temperature records. Parts of upstate New York, Vermont, New Hampshire, and Maine received up to two inches (50.80 mm) of ice and gusty winds, which brought down trees and power lines. Around 66,000 customers lost power in upstate New York and over 100,000 customers lost power in Maine, with some left without power or heat for 10 days. The Vermont Electric Cooperative estimated the cost of cleanup to be around $6.5 million. According to the Watertown Daily Times, the storm caused thick ice conditions on the St. Lawrence Seaway, which delayed ship traffic. In other areas, such as western New York, melting snow and up to 2.50 inches (63.50 mm) of rain caused flooding.
- For more information, please go to the Northeast Regional Climate Center Home Page.
- Midwest Region: (Information provided by the Midwest Regional Climate Center)
- December temperatures across the Midwest ranged from just above normal in Ohio and Kentucky to well below normal in Minnesota, particularly northern Minnesota. Statewide values were 0.8 degrees F (0.4 C) above normal in Kentucky and 0.4 degrees F (0.2 C) above normal in Ohio while colder temperatures were recorded to the northwest with Minnesota (7.9 degrees F, 4.4 C), Wisconsin (6.5 F, 3.6 C), Iowa (5.3 F, 2.9 C), and Michigan (5.0 F, 2.8 C) well below normal for the month. Minnesota ranked as the 8th coolest December in 119 years of records while Wisconsin and Michigan each ranked as the 11th coolest. Many northern Minnesota locations recorded their coldest December or were among the 10 coldest. Annual temperature values for 2013 were slightly cooler than normal and the spatial pattern was similar to the December spatial pattern. Ohio was just above normal (0.1 degrees F, 0.1 C) and Minnesota (-1.8 F, -1.0 C), Iowa (-1.3 F, -0.7 C), and Wisconsin (-1.3 F, -0.7 C) recorded the coldest annual values.
- December precipitation was well below normal in Iowa (52 percent of normal) and below normal in Missouri and Illinois (both 85 percent of normal). The other six states were above normal for the month with Minnesota being the wettest compared to normal (165 percent of normal). Snowfall was above normal for much of the region, with largest departures in the northern half of the region, with totals topping 24 inches (61 cm) across northern halves of Minnesota, Wisconsin, and Michigan. The snow fell in several storms that moved across the Midwest during the month. The paths of the storms varied but the Upper Midwest was hit repeatedly. A stalled front that was draped across the southeast portion of the Midwest on the 20th through the 22nd brought heavy rains to parts of Kentucky, Indiana, and Ohio. Many rivers rose to their highest level in several year following the deluge which also brought severe weather to those states. Annual precipitation values for 2013 topped normal for all nine states using preliminary statewide estimates. Statewide annual values ranged from 104 percent of normal (Iowa) to 122 percent of normal (Michigan).
- Record temperatures were mostly record lows in the region during December. Warm advection ahead of the stalled front on the 20th – 22nd brought some record highs to Kentucky and Ohio but several systems dropped temperatures to record lows during the month. Record lows were recorded in all states except Ohio and outnumbered record lows about two to one.
- Severe weather in December was limited to the 21st of the month in the Midwest. A couple hundred of wind damage reports, mostly in Kentucky and Ohio, were reported along with three EF1 tornadoes in Kentucky. The tornadoes all damaged numerous trees along with roofs, barns, and other outbuildings.
- For details on the weather and climate events of the Midwest, see the weekly summaries in the Midwest Climate Watch page.
- Southeast Region: (Information provided by the Southeast Regional Climate Center)
- Monthly average temperatures for December were above normal across the Southeast region. The greatest departures were found across the Florida Peninsula and coastal sections of Georgia and South Carolina, where monthly temperatures were between 5 and 6 degrees F (2.8 and 3.3 degrees C) above normal. Miami, FL (1895-2013) recorded its second warmest December on record, while Fort Myers, FL (1902-2013), Orlando, FL (1892-2013), and Daytona Beach, FL (1937-2013) all recorded their third warmest Decembers on record. Elsewhere across the region, monthly temperatures were 3 to 4 degrees F (1.6 to 2.2 degrees C) above normal across much of the Carolinas and Virginia, while temperatures were 1 to 2 degrees F (0.5 to 1.1 degrees C) above normal across much of Georgia and Alabama. Monthly temperatures were also above normal across Puerto Rico, with San Juan (1898-2013) recording its second warmest December on record. Temperatures were near normal across the U.S. Virgin Islands. Two waves of warm weather were observed across the Southeast in December. The first occurred from the 5th to the 7th of the month, as maximum temperatures reached 80 degrees F (26.7 degrees C) as far north as southern Virginia. Over 100 daily high maximum temperature records were tied or broken during this period, including some monthly records. Savannah, GA (1871-2013) and Milledgeville, GA (1898-2013) recorded a maximum temperature of 83 degrees F (28.3 degrees C) on the 6th and 7th, respectively, which tied for the warmest temperature recorded on any December day at either location. The second wave of warm weather occurred just prior to the Christmas holiday, as maximum temperatures were as much as 20 to 30 degrees F (11 to 16 degrees C) above normal across the northern half of the region. Over 250 daily high maximum temperature records were tied or broken from the 21st to the 23rd of the month. Several monthly records were also tied or broken. Augusta, GA (1873-2013) recorded a maximum temperature of 83 degrees F (28.3 degrees C) on the 21st, which broke the previous record of 82 degrees F (27.8 degrees C) that was last recorded just two weeks earlier on the 6th. Overnight temperatures were also exceptionally warm during this period, as over 300 daily high minimum temperature records were tied or broken across the region.
- Precipitation in December was variable across the Southeast region. Monthly totals were generally 2 to 4 inches (50.8 to 101.6 mm) above normal across the interior of the region, while much of Florida (except the extreme southeast part of the state), as well as coastal sections of Georgia and the Carolinas, were 1 to 3 inches (25.4 to 76.2 mm) below normal. Monthly precipitation was also variable across Puerto Rico, with above normal rainfall along the coast and below normal rainfall in the interior of the island. The wettest locations in the Southeast were found in a swath extending from central Alabama through northern Georgia, South Carolina, and southwestern North Carolina, where monthly totals exceeded 10 inches (254 mm) in places. Much of this precipitation fell from the 22nd through the 24th of the month as a slow-moving frontal boundary tracked across the eastern U.S. Daily rainfall totals were generally between 2 and 4 inches (50.8 and 101.6 mm), with higher amounts exceeding 5 inches (127 mm) across parts of central Alabama and northern Georgia. An additional 1 to 3 inches (25.4 to 76.2 mm) of rain fell across much of the region on the 28th and 29th as a low pressure system tracked northward out of the Gulf of Mexico. Brevard, NC (1931-2013) recorded its wettest December on record with 14.77 inches (375 mm) while nearby Calhoun Falls, SC (1919-2013) recorded its third wettest December on record with 9.87 inches (251 mm). Macon, GA (1892-2013) also recorded its third wettest December on record with 9.04 inches (230 mm). Monthly precipitation was above normal across the U.S. Virgin Islands with totals ranging from 7 to 10 inches (178 to 254 mm). In contrast, the driest locations in December were found across the Florida Peninsula, where monthly precipitation totals were less than 25 percent of normal. Several locations recorded less than an inch (25.4 mm) of precipitation, most notably Fort Myers, FL (0.50 inches; 12.7 mm), Naples, FL (0.32 inches; 8.1 mm) and Orlando, FL (0.27 inches; 6.9 mm). Monthly snowfall totals ranged from 1 to 5 inches (25.4 to 127 mm) across the Southern Appalachian Mountains and parts of northern Virginia. In addition, up to 0.50 inches (12.7 mm) of ice and sleet accumulated across parts of western and central Virginia on the 8th and 9th of the month. Minor icing and some slick roadways were also reported across the foothills and western Piedmont of North Carolina.
- On the 14th of the month, an EF-1 tornado caused mostly minor damage to a few homes and structures in Palm Coast, FL, located north of Daytona Beach in Flagler County. There were 13 reports of damaging thunderstorm winds scattered across parts of Alabama, Florida, Georgia, and the Carolinas on five other days throughout the month. Two homes in the Atlanta, GA area were damaged from lightning strikes on the 22nd of the month.
- The above normal precipitation in December helped eliminate the broad areas of abnormally dry (D0) conditions that had stretched across much of Virginia, the Carolinas, and central Georgia. Small ribbons of D0 remained across extreme eastern sections of North Carolina, Georgia, and southern Alabama, and expanded slightly across central portions of Florida where precipitation deficits were the greatest. The dry conditions in Florida helped farmers complete their harvests and continue their planting of winter crops. While the lack of moisture continued to limit the growth of many fruit crops, the warm temperatures helped accelerate vegetable growth across much of South Florida. The heavy rains across Georgia forced some reservoirs, including Strom Thurmond Lake near Augusta, to temporarily close their recreation areas, boat ramps, and fishing piers due to high water levels.
- After two years of exceptionally warm mean annual temperatures, most of the Southeast experienced near normal mean temperatures in 2013. One exception was Miami, FL (1895-2013), which tied its fourth warmest year on record. The big story in 2013 was the heavy precipitation and its impact on numerous economic sectors and human life in the region. Several locations recorded their wettest year on record, including Macon, GA (1892-2013) and Asheville, NC (1869-2013). Macon recorded 72.91 inches (1852 mm), which broke the previous record of 67.80 inches (1722 mm) set in 1929. Asheville recorded 75.23 inches (1911 mm), which shattered the previous record of 64.91 inches (1649 mm) set in 1973. Five official cooperative observer stations in the Southern Appalachians recorded over 100 inches (2540 mm) of precipitation in 2013. The greatest total was recorded at Lake Toxaway, NC (1952-2013) with 128.69 inches (3269 mm). Brevard, NC (1931-2013) and Mount Mitchell, NC (1980-2013) recorded their wettest years on record with 112.14 and 101.25 inches (2848 and 2572 mm), respectively, while Highlands, NC (1879-2013) recorded its second wettest year with 111.57 inches (2834 mm). Helen, GA (1956-2013) eclipsed the century mark for the first time in its period of record with 101.42 inches (2576 mm), which also marked the third highest annual total ever recorded at an official cooperative station in the state of Georgia. In addition, numerous other locations recorded one of their top 5 wettest years on record, including Greenville-Spartanburg, SC (1884-2013) and Atlanta, GA (1878-2013).
- For more information, please go to the Southeast Regional Climate Center Home Page.
- High Plains Region: (Information provided by the High Plains Regional Climate Center)
- Several Arctic blasts led to a bitterly cold end to the year. The first cold air outbreak of the month brought temperatures that were 20.0-30.0 degrees F (11.1-16.7 degrees C) below normal to the Region. Wind chills were dangerously low during this timeframe. Although there were a few reprieves from the bitterly cold air, temperatures across the majority of the High Plains Region were ultimately well below normal. North Dakota and South Dakota had the largest departures with temperatures ranging from 6.0-12.0 degrees F (3.3-6.7 degrees C) below normal. Temperature departures of 3.0-6.0 degrees F (1.7-3.3 degrees C) below normal were common across the remaining states in the Region. While not record breaking, some locations did rank in the top 10 coolest Decembers on record. One example was Grand Forks, North Dakota which had its 3rd coolest December with an average temperature of -0.1 degrees F (-17.8 degrees C). Although this was 11.6 degrees F (6.4 degrees C) below normal, it was just shy of the record of -1.0 degree F (-18.3 degrees C) set back in 1917 (period of record 1893-2013). Another top 10 location was Aberdeen, South Dakota. With an average temperature of 6.5 degrees F (-14.2 degrees C), Aberdeen had its 4th coolest December (period of record 1893-2013). The record of -0.5 degrees F (-18.1 degrees C) occurred in 1983. The bitterly cold weather did have impacts on travel and local business in North Dakota, according to the Grand Forks Herald. As temperatures plummeted, many folks were stranded in their vehicles when their diesel fuel turned to gel. One towing company indicated that business had quadrupled from the usual. Batteries and cold weather clothing were also in high demand. In addition, oil production in western areas of the state slowed due to the frigid temperatures.
- This month, the High Plains Region was generally wetter in the northern areas and drier in the southern areas. The heaviest precipitation was confined to North Dakota, South Dakota, and Wyoming where liquid equivalent precipitation totals ranged from near normal up to 400 percent of normal. Bismarck, North Dakota had its 9th wettest December on record by picking up 1.26 inches (32 mm) of liquid equivalent precipitation (period of record 1874-2013). Bismarck also had its 9th snowiest December on record. Other locations also ranked in the top 10 snowiest Decembers. For instance, Pierre, South Dakota had its 4th snowiest December with 14.2 inches (36 cm). Pierre's record amount of 31.3 inches (80 cm) occurred in 1951 (period of record 1897-2013). In addition, Grand Forks, North Dakota had its 5th snowiest December on record with 22.8 inches (58 cm). The old record of 30.2 inches (77 cm) fell in 1996 (period of record 1893-2013). Some areas of the Region only received light precipitation throughout the month. A large area stretching from eastern Colorado into western Kansas and across Nebraska received at most 25 percent of normal precipitation. Isolated areas picked up little to no precipitation with totals of 5 percent of normal or less. Luckily, December is typically one of the driest months of the year, so below normal precipitation at this time of the year does little to impact the ongoing drought situation across Nebraska, Kansas, and Colorado. Garden City, Kansas was one of these dry spots and with only 0.01 inches (0.3 mm) of liquid equivalent precipitation, it tied for 4th driest December on record (period of record 1947-2013).
- As expected this time of year, changes in drought conditions in the High Plains Region were minor, according to the U.S. Drought Monitor. Approximately 20 percent of the Region was in moderate (D1) to exceptional (D4) drought at the end of the month, which was a slight increase from 19 percent at the end of November. One year ago, 93 percent of the Region was in drought with about 27 percent in the D4 designation - what a difference a year makes! Although there were significant improvements in drought conditions throughout 2013, little change is expected over the winter. Since the winter is typically the driest part of the year in the High Plains Region, no improvements in drought conditions are expected over the next few months. According to the U.S. Seasonal Drought Outlook released December 19th, current drought conditions are expected to persist across Nebraska, Kansas, Colorado, and Wyoming through March 2014. Additionally, drought development is expected in western Colorado.
- For more information, please go to the High Plains Regional Climate Center Home Page.
- Southern Region: (Information provided by the Southern Regional Climate Center)
- The month of December was a slightly cooler than normal month for much of the Southern Region, with the exception of Tennessee and eastern Mississippi, which experienced a slightly warmer than normal month. Temperatures in Arkansas and Louisiana averaged between 0 to 2 degrees F (0 to 1.11 degrees C) below normal. This was also the case over most of Texas, expect in the north where some stations averaged between 4 to 6 degrees F (2.22 to 3.33 degrees C) below normal. Central Oklahoma also averaged between 4 to 6 degrees F (2.22 to 3.33 degrees C) below normal. The statewide average temperatures are as follows: Arkansas reported 39.70 degrees F (4.28 degrees C), Louisiana reported 49.60 degrees F (9.78 degrees C), Mississippi reported 46.40 degrees F (8.00 degrees C), Oklahoma reported 34.80 degrees F (1.56 degrees C), Tennessee reported 40.40 degrees F (4.67 degrees C), and Texas reported 44.60 degrees F (7.00 degrees C). For Oklahoma, it was their sixteenth coldest December on record (1895-2013), while Texas experienced its eighteenth coldest December on record (1895-2013). It was also the twenty-third coldest December on record (1895-2013) for the state of Arkansas. All other state rankings fell within the two middle quartiles.
- December precipitation totals in the Southern Region varied spatially, with parts of the region receiving anomalously high amounts of precipitation, while other parts remained quite dry throughout the month. Areas of above average precipitation include: the extreme south of Texas, the western Texas panhandle, west central Texas, northern Arkansas, and eastern Tennessee. Precipitation totals in these regions varied from 130 to over 200 percent of normal. Conversely, areas of dryness included: much of Oklahoma, south eastern Texas, and most of the state of Louisiana. Precipitation totals in those regions varied from half of normal to under 5 percent of normal. The statewide average precipitation totals are as follows: Arkansas recorded 6.25 inches (158.75 mm), Louisiana recorded 3.72 inches (94.49 mm), Mississippi recorded 5.55 inches (140.97 mm), Oklahoma recorded 1.11 inches (28.19 mm), Tennessee recorded 6.35 inches (161.29 mm), and Texas recorded 1.46 inches (37.08 mm). For Arkansas it was their twentieth wettest December on record (1895-2013), while for Louisiana, it was their twenty-first driest December on record (1895-2013). All other state rankings fell within the two middle quartiles.
- Drought conditions over the month of December remained relatively unchanged, with northwestern Texas and western Oklahoma experiencing moderate to severe drought conditions. A small area of extreme and exceptional drought persists along the southwestern Oklahoma-Texas border.
- A cold front on the day of December 21, 2013 resulted in several tornadoes in the areas of eastern Arkansas, northwestern Mississippi, and northern Louisiana. A tornado in St. Francis County, Arkansas resulted in one fatality and three injuries. Reports indicate that two homes were completely destroyed, with three homes enduring significant roof damage. Another fatality occurred in Caohoma County, Mississippi.
- In Texas, an ice storm occurred in the Dallas-Fort Worth Metroplex. The storm hit overnight on December 5, 2013 and coated areas with between one and four inches of ice, completely shutting down the region. The ice was responsible for the cancellation of over 1,100 flights out of DFW international Airport, the shutdown of nearly every major interstate into and out of the city, and the loss of power to over 260,000 people. Preliminary estimates believe there to be over 1 billion dollars of roadway damage to the Metroplex and $30 million in other damages. The same system brought deadly, multicar pile-ups to El Paso, and another ice storm later in the month did the same to Amarillo. The cold weather also contributed to a variety of agricultural and ecological impacts around the state. Short-term dryness in the Panhandle is causing some concern over winter wheat, as snowfall has been below average, but cooler temperatures are helping prevent moisture loss. Grains in central Texas, in spite of the drought, saw record high production levels, leading to optimistic forecasts for next year. Ecologically, the cold weather has been hard on plants and wildlife, including 200 cold-shocked sea turtles that needed rehabilitation and millions of dollars in damage to trees during the month's multiple ice storms (Information provided by the Texas Office of State Climatology).
- For more information, please go to the Southern Regional Climate Center Home Page.
- Western Region: (Information provided by the Western Region Climate Center)
- December began with an unusually early and severe cold episode over much of the West, with daily average temperatures within the month ranging from very far below to much above normal. Persistent high pressure developed over the West Coast and helped guide storms towards the Rockies and inland West while keeping the coastal states drier than normal.
- A drier than normal December solidified 2013 as the driest calendar year since at least 1895, from the Los Angeles Basin northward to about Eugene Oregon, and in parts of Idaho. Downtown San Francisco received 5.59 in (142 mm), the driest year in the longest climate record in the state (164 years), and only 24% of normal annual precipitation. Further north, Shasta Dam received no December precipitation for the second time in a 71-year record. Precipitation there totaled 16.39 in (416 mm) for 2013, far below the previous record low of 27.99 in (711 mm) set in 1976. In Southern California, downtown Los Angeles received 0.24 in (6 mm) of rainfall this month, only 9% of normal. A scant 3.60 in (91 mm) of rain fell at this location during 2013, the lowest annual precipitation since records began in 1877 (previously 4.08 in / 104 mm in 1947 and 1953). Dry conditions prevailed in Oregon and Washington as well. Medford, Oregon logged its driest December since records began in 1911 with 0.36 in (9 mm) of rainfall, as well as its driest calendar year, with a total of 8.99 in (228 mm). In eastern Washington, Ephrata reported its driest December in a 65-year record with 0.02 in (0.5 mm) precipitation. Snowpack conditions were dismal in the Sierra Nevada and Cascades at month's end, with snow water equivalent values at <50% of median. Snow water equivalent values in the Intermountain West were at roughly 50-75% of median. The lack of snow impacted ski resorts over the holiday season, many operating only a fraction of their terrain or still closed. Snowpack was near to slightly above normal throughout the Rocky Mountains.
- Wetter than normal conditions were observed across central Nevada, in the Northern Rockies, and in eastern Montana. Ely, Nevada recorded 0.99 in (25 mm) precipitation, 168% of normal and the 22nd wettest December in a 121-year record. Precipitation in Billings, Montana totaled 1.63 in (41 mm) for the month, 307% of normal and the wettest December since records began in 1894. Casper, in central Wyoming, saw its 3rd wettest December in a 66-year record with 1.2 in (30 mm) precipitation.
- Except for southern California, the West was mostly considerably cooler than normal this month. At Burns, Oregon, the minimum temperature of -30 F (-34 C) on the 8th exceeded all previous values for any month since records began in 1939. The monthly average of 19.3 F (-7.1 C) was also the 4th coldest December at Burns. In Winnemucca, Nevada, temperatures averaged 18.1 F (-7.7 C) for the month, the second coldest December in a 137-year record. The December average temperature in Boise, Idaho was 23.9 F (-4.5 C), 6.8 F (3.8 C) below normal and the 6th coldest December in a record that began in 1940. Salt Lake City, Utah, averaged 24.6 F (-4.1 C) for the month, the 8th coldest December in an 86-year record. Daily mean temperature anomalies ranged from -51 F / -28.3 C on the 7th to +23 F / +12.8 C on the 27th at Havre, and spanned a range from -47 F / -26.1 C to +26 F / +14.4 C on the same two days at Great Falls, both in Montana.
- December temperatures averaged slightly above normal in some Southwest locations. Long Beach, California recorded three consecutive daily record highs of 83 F, 83 F (28.3 C), and 84 F (28.9 C) on December 25, 26, 27, respectively, and had a monthly average temperature 1.7 F (1 C) above normal. Records at Long Beach began in 1949. Temperatures at Tucson, Arizona averaged to 53.2 F (11.8 C) for December, 1.3 F (0.7 C) above normal. Only one day with sub-freezing temperatures was observed at Tucson this month, the fewest number of sub-freezing December days since 2000.
- Further north, precipitation departures from normal were variable throughout Alaska, though considerably above normal along the North Slope. Barrow saw its wettest December on record with 1.17 in (30 mm), 836% of normal. Temperatures were warmer than normal along the western and northern coasts, and generally cooler than normal in the Interior. In Cold Bay, temperatures averaged to 38 F (3.3 C) for the month, 7.7 F (14.3 C) above normal and the warmest December in a 64-year record. Further south, windward locations on Hawaii's Big Island, Maui, and Kauai received above normal precipitation. Hilo logged 20.2 in (513 mm) for the month, the 10th wettest December in a 65-year record.
- December 15-20: Out-of-season Pfeiffer Fire in Big Sur, California: Extremely dry conditions in California provided highly flammable fuels for a fire that ignited in Big Sur, an area on the coast of central California. The fire charred 917 acres (371 hectares) and destroyed 34 homes. Fires are not uncommon in Big Sur, but typically occur between May and October.
- December 4-13: Sub-freezing temperatures threaten California citrus: California's San Joaquin Valley experienced multiple days of hard freeze that likely caused significant damage to citrus. Impacts will be evaluated as the fruits develop.
- December (all month): Poor air quality for interior valleys: Strong inversions developed this month in inland valleys such as Salt Lake City, Utah; Boise, Idaho; Reno, Nevada; and California's Central Valley, trapping air pollutants near the surface. In Salt Lake City, 10 days this month had air quality deemed "unsafe for sensitive groups" (24-hour PM 2.5 between 35.4 ug/m3 and 55.4 ug/m3) and one day of "unhealthy" air quality (24-hour PM 2.5 between 55.5 ug/m3 and 150.4 ug/m3). The 5-year average for Salt Lake City in December is 4 days "unsafe for sensitive groups" and 0 days "unhealthy."
- For more information, please go to the Western Regional Climate Center Home Page.
For additional details about recent temperatures and precipitation across the U.S., see the Regional Highlights section below and visit the Climate Summary page. For information on local temperature and precipitation records during the month, please visit NCDC's Records page.
These regional summaries were provided by the six Regional Climate Centers and reflect conditions in their respective regions. These six regions differ spatially from the nine climatic regions of the National Climatic Data Center.