Monday, July 25, 2011

U.S. Summer Heat Records Continue Overwhelming Cold Records By Over 8:1

They haven't matched the incredible pace of June records, but U.S. temperature extremes this summer continue to overwhelmingly favor hot records vs. cold records. Through the 23rd, the number of daily high temperature records reported by the National Climatic Data Center (NCDC) in July outnumbered low temperature records by a ratio of over 5 to 1. Combined with June's torrid ratio of nearly 11 to 1, the ratio for the summer to date stands at 8.3 to 1. For the year 2011 to date, as well as the last 12 consecutive months, the ratio has risen to 2.6 to 1.

December 2010 is now the only month in the past 17 consecutive months with more cold records than heat records, and that was only by the slim margin of about 1.5 to 1.

Results have been particularly dramatic for longer-term records. A total of 65 all-time July monthly heat records have been set so far vs. only 8 monthly cold records, for a ratio of over 8 to 1. Out of those July monthly records, 44 were all-time record highs for any month.

Image (click to enlarge):
Monthly ratios and monthly total numbers of daily high temperature and low temperature records set in the U.S. for July 2010 through July 23 2011; Cumulative excess of heat records vs. cold records since January 2010. Data from NOAA National Climatic Data Center, 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.

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