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7 PM Update: Added chart of ratios from previous decades for comparison.
As previously reported, U.S. daily high temperature records were dominating cold records in July by a ratio of over 5 to 1, based on preliminary data from the National Climatic Data Center. A surge of heat records in the final week of the month has pushed the total ratio to 6.1 to 1. For the summer as a whole (June and July combined), the ratio has increased to 8.4 to 1. This also increases the year-to-date ratio to 2.7 to 1.
Out of the 1601 daily high temperature records broken in July, 49 were all-time records for any day of any month. Combined with the updated count of 20 all-time records in June, this gives a total of 69 so far this summer. In comparison, only 8 all-time cold records were set in all 3 months of last winter combined.
Preliminary data from ESRL/NOAA shows that nearly all of the U.S. east of the Rockies was above average (1981-2010 baseline) with the most extreme temperature values from northern Texas through Oklahoma and Kansas.
Images (click to enlarge):
- Monthly ratios of daily high temperature to low temperature records set in the U.S. for July 2010 through July 2011. Data from NOAA National Climatic Data Center, 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.
- Decadal average ratios of heat records to cold records, from University Corporation for Atmospheric Research
- Preliminary July 2011 U.S. temperature departure from 1981-2010 average from ESRL.
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