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Here’s How Much U.S. Summers Have Warmed Since 1970

June is here, so let the great debate over the Song of the Summer begin! Will this summer’s earworm come from a pop stalwart like Katy Perry or a newcomer like Iggy Azalea? Radio and Spotify listeners around the country will decide. One summer trend that’s not up for debate, though: the season has been getting hotter across the U.S. since 1970.

A map showing summer temperature trends in 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.

The notable blue spot in a sea of red is the Upper Midwest, where substantial parts of Iowa and the Dakotas have seen a slight cooling trend since 1970. Interestingly, that region is actually home to some of the fastest-warming states when you look at the change in annual average temperatures. Winters in particular have warmed dramatically there over the past 40 years.

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, it's impacts on weather patterns in the U.S. don't generally become pronounced until fall.

You may now return to debating the merits of “Fancy."

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By Joseph (Sussex,NJ 07461)
on June 3rd, 2014

Why is it colder than normal everyday this year except for one , durring the solar maximum

Reply to this comment

By Jim (Raleigh, NC)
on June 7th, 2014

Wasn’t the 70’s a particular cool period?  I remember concerns of an impending ice age in the 70’s, so to compare our temp now to what was considered a very cold period of time seems strange and more political than scientific.

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By Chris A (Charleston SC)
on June 30th, 2014

Must every article somehow reference global warming or climate change. Our climate is dynamic and after the dire warnings of the coming ice age 30 years ago now we have the dire warnings for the opposite. At some point people have to realize that not every temperature variation is an apocalypse. The sun has cycles and so does the Earth. Screaming the sky is falling everytime the weather changes is counter-productive. Has mankind had an impact on the climate? Maybe but the inconvenient truth is since 1970 there has been a 35% increase in the world population and every one of these people breathe out carbon dioxide. It only makes sense there’s more of it in the atmosphere.

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