The Heat Parade: December Heat Records Exceed Cold By 80%;Annual Ratio Jumps to 2.8 to 1 in 2011

Aided by a strong warm surge toward the end of the month, new U.S. daily high temperature records exceeded daily cold records in December by a ratio of 1.8 to 1, a margin of 80%. The overwhelming excess of heat records continued into New Year's Day, when the 116 high maximum records set or tied absolutely crushed the one lonely low minimum record (at a co-operative station 3 miles northeast of Marlin Texas).

The December high/low record ratio was equal to the ratio for the preceding fall season, but the extreme summer ratio of over 11 to 1 pushed the annual value to 2.8 to 1, well above the 2.3 to 1 in 2010. Although January's heat records were only about 4% more numerous than the cold records, the ratio was over 1 for every individual month in 2011. The last time cold records exceeded heat records in a month was a year ago, in December 2010.

Preliminary data from NOAA/ESRL show that U.S. December average temperatures were noticeably below normal only in the desert southwest and parts of Texas. Elsewhere, temperatures were as much as 6°C (nearly 11°F) above average in North Dakota and western Minnesota. To the north, temperatures ranged even higher relative to average in western Canada, as high as 8°C in some areas. December temperatures were also quite warm across nearly all of continental Europe.

For 2011 as a whole, U.S. temperatures averaged above the new 1981-2010 climatological base nearly everywhere east of the Rocky Mountains. The heat bullseye was centered in the drought areas of Oklahoma and northern Texas. The coldest areas relative to average were in the Pacific Northwest and California.

Images (click to enlarge):
- Monthly ratio of daily high temperature to low temperature records set in the U.S. for December 2010 through December 2011, seasonal ratio for summer and fall 2011, and annual ratio for 2011 and 2010;
- Monthly total counts of daily high temperature and low temperature records set in the U.S. for December 2010 through December 2011
- U.S. December 2011 temperature departure from climatological average
- Europe December 2011 temperature departure from climatological average
- U.S. 2011 annual temperature departure from climatological average
CapitalClimate charts from NOAA/NCDC data, background image © Kevin Ambrose (www.weatherbook.com). 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.
U.S. and Europe monthly and annual temperature maps from NOAA/NCEP via ESRL