June 1 marked the first day of meteorological summer in the Northern Hemisphere, time for beach trips, barbecues and sweating through summer’s heat. This hottest of all the seasons is getting even hotter as the planet warms from the increase in greenhouse gases in the atmosphere.

Meteorological summer differs from astronomical summer, which is marked by the tilt of the Northern Hemisphere towards the sun, meaning it’s the hemisphere receiving the most solar energy. Meteorological summer, meanwhile, consists of the three months of the year with the warmest average temperatures, the months of June, July, and August.

Summer temperature trends

Summer temperature trends for each NOAA/NCEI climate division since 1970.

As the planet warms, those summer temperatures are rising. Not only that, but there is also an increase in the number days with extreme heat and instances when the temperatures don’t cool off as much at night. This combination raises the risks of heat-related illnesses like heat exhaustion and heat stroke. And for those with air conditioning, cooling bills will begin to climb.

Not all locations in the U.S. are heating up at the same rate, though. Some of the greatest warming is occurring in Texas, the Southeast, and the West. A small sliver of the Upper Midwest and Northern Plains has not shown a warming trend in the summer, but those locations are warming much more during the winter.

An analysis of 166 cities spread across the country by Climate Central’s Climate Matters program indicated that 92 percent of those sites have been trending warmer since 1970. There is a scattering of locations from Boise, Idaho, to Columbia, S.C., that have warmed more than 3°F (1.7°C) in that time, but the most pronounced warming is clustered in Texas, where several sites have warmed about 4°F (2.2°C). These include El Paso, Laredo, McAllen, and Odessa.

NOAA summer temperature outlook

NOAA summer temperature outlook.


Through the spring, 2017 has already been much warmer than normal for the U.S. According to the National Oceanic and Atmospheric Administration (NOAA), the first four months of 2017 have been the second warmest such period on record, surpassed only once by the same period in 2012. In every year so far this century, except for 2014, this four-month period has been warmer than the 20th century average.

The summer temperature outlook from the NOAA Climate Prediction Center suggests this summer will continue the trend. The most likely places to be hotter than normal are along the eastern third of the U.S., the Gulf Coast, the West Coast, and Alaska. And no place is forecast to be cooler than normal.