Spectacularly Warm Start to December in U.S.; Above-Average Temperatures From Coast to Coast

As noted last week, December got an exceptionally warm start in the contiguous 48 states of the U.S., and that trend has continued even more strongly through the first third of the month. Except for 2 weeks in October, nationwide temperatures have been warmer than average every week in 2012 and for 50 of the last 52 weeks.

For December 1-10, temperatures have averaged above normal everywhere from coast to coast. In the calender week ending December 8, of the 215 first-order National Weather Service (NWS) stations reported weekly by the Climate Prediction Center, 1 was missing (Glasgow, Montana), none were equal to or colder than average, only 1 was 1° above average (Key West, Florida), 2 were 2° above, and all the rest were at least 3° above. Over half of the reporting locations were 10° or more warmer than average, and 15 of them across 10 states (AL, AR, IA, IL, IN, KY, MO, MS, SD, TN) had departures of 15° or more for the week.

Even in a year with very warm extremes in January, March, and July, this was some serious heat. For the country overall, the average for all 214 NWS stations was slightly over 10.0° above normal, and the National Climatic Data Center (NCDC) geographically adjusted average was 8.9° above average.

Temperatures have not only been consistently warm over a wide area, but many individual locations have set records. For the first 10 days of December, new daily record high temperatures have outnumbered record lows by a ratio of 92 to 1. For the 48 contiguous states, the ratio was an incredible 132 to 1, since 3 out of the 10 low records were in Alaska and Hawaii. During the entire week of December 2-8, not a single low temperature record was tied or broken in any of the 50 states, according to NCDC reports. With 3 weeks remaining in the year, the cumulative ratio of heat records to cold records for 2012 has reached 6.0 to 1, more than double the ratio in 2011.

Images (click to enlarge):
- Weekly average U.S. temperature departures from normal for 2012, through December 8 (20121208); CapitalClimate chart from NOAA/NCDC data
- Weekly average NWS station temperature departures from normal, week ending December 8, 2012; stations listed alphabetically by state and 3-character station identifier; CapitalClimate chart from NWS data
- December 1-10, 2012 U.S. temperature departure from average, from High Plains Regional Climate Center
- Monthly ratio of daily high temperature to low temperature records set in the U.S. for November 2011 through December 2012 to date, seasonal ratios for summer 2011 through fall 2012, and annual ratios for 2012 and 2011.
CapitalClimate chart from NOAA/NCDC data, background image © Kevin Ambrose. Includes historical daily observations archived in NCDC's Cooperative Summary of the Day data set and preliminary reports from Cooperative Observers and First Order National Weather Service stations. All stations have a Period of Record of at least 30 years.