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Summer 2010 set temperature records across the country and around the world. NRDC's analysis of June, July, and August 2010 US temperature data from the National Oceanographic and Atmospheric Administration's (NOAA's) Historic Climatology Network reveal that this summer set heat records in many parts of the country. In fact, of the 1,218 weather stations in the contiguous United States, with data going back to 1895, 153 locations recorded their hottest summer on record and nearly one in three stations recorded average temperatures among their five hottest on record.

Even more telling is that nighttime lows were the hottest ever recorded at nearly one in four weather stations in NOAA's Historic Climatology Network. This means that at 278 stations the average nighttime low temperatures for June, July and August 2010 were hotter than at any time since 1895. More than half the stations recorded average nighttime low temperatures among their five hottest on record. Nighttime temperatures are more sensitive to the buildup of heat-trapping pollution in the atmosphere than daytime temperatures because increases in atmospheric aerosols and cloud cover have counteracted some of the warming effect of greenhouse gases during the day. Hot, stagnant nights can prove even more harmful than daytime highs as vulnerable populations (particularly the elderly) are unable to cool down and get relief from the stress of the daytime heat.

Summer 2010 Temperatures from Weather Stations in NOAA's Historic Climatology Network, by State

Record Temperatures Seen in 37 States: State Maps and Table of Weather Stations

While it is difficult to know for certain how many people experienced health effects of one kind or another due to record-high temperatures this summer, it is possible to estimate how many people may have been exposed to extreme temperatures by counting the populations in those counties where average and nighttime temperature records were set. The accompanying tables show how many people in each state where records were set live in counties where one or more weather stations recorded record average or nighttime summer temperatures. This examination reveals that nationwide, over 28.5 million people live in counties where this summer's average temperature set records, and over 36 million people live in counties where the hottest summer nights were recorded this summer. (Record-setting temperatures source: NRDC fact sheet "Hottest Summer Ever". Population data source: http://www.census.gov/popest/datasets.html.)

• State Population Residing in Counties Where Summer Average Temperature Records Were Set (pdf)
• State Population Residing in Counties Where Summer Nighttime Temperature Records Were Set (pdf)

The record heat experienced in the United States in the summer of 2010 is no isolated event. Global temperature data compiled by NASA show that the first seven months of 2010 was the hottest such period on record. This comes on top of the warmest decade on record (2000-2009), which surpassed the previous record set by the 1990s, which itself supplanted the 1980s as the warmest decade on record at that time.

 

last revised 9/14/2010