How Much U.S. Summers Have Warmed Since 1970

June is here and one summer statistic has already emerged; the season has been getting hotter across the U.S. since 1970.

Nationwide, the summer warming trend averages out to a little more than 0.4°F per decade since 1970. The places warming the fastest also happen to be some of the hottest places in the country, with a large chunk of the Southwest and all of Texas warming more than 1°F per decade.

Of the 344 climate divisions, which are set by the National Climatic Data Center and divide the country into climatically-similar zones, less than 10 percent have seen a summer cooling trend. In general, every state in the lower 48 has warmed since 1970 and the most recent decade was the warmest on record for the country.

Those trends are consistent with the overall warming that has been observed for the planet as greenhouse gases emitted by humans build up in the atmosphere.

For this summer, the Climate Prediction Center (CPC) is forecasting a large "U" of areas where above normal temperatures are more likely running from down the West Coast across the South and back up the Eastern Seaboard.

CPC also forecasts below normal temperatures are likely in the Upper Midwest based overarching climate conditions. While El Niño is likely to form this summer, its impacts on weather patterns in the U.S. won't generally become pronounced until fall.