The last day of August marked the end of meteorological summer — the three months of the year that are the hottest in the northern hemisphere: June, July and August.

With summer at an end, a review of the average summer temperature for many areas across the U.S. shows, not surprisingly, that as the concentration of greenhouse gases climbs, more and more areas are finishing the summer hotter than normal. In some cases, much hotter than normal.

Huge swaths of the country were much warmer than normal including the entire Eastern Seaboard, Ohio River Valley and Southwest. The Upper Midwest and Southern Plains were hot, but not nearly as hot relative to normal.

Alaska also continued its prolonged run of extremely abnormal high heat, with Anchorage having an average summer temperature of 60.8°F (16°C), breaking the previous record of 60.2°F (15.7°C) set just last year.

While the full National Oceanic and Atmospheric Administration nationwide analysis will be released on Sept. 8, a preliminary analysis from Climate Central indicates that several cities had their hottest summer on record. And unlike last year, when there was a small area of the Midwest that was cooler than normal, nearly all of the country was near normal or hotter this year.

The hot and sticky summers in the Southeast were especially so this year. Charleston, Columbia, New Orleans, and Savannah all had their hottest summer on record.

In general, summers have been warming in the U.S. as a result of climate change. A few pockets in the Upper Midwest have not seen an increase in average summer temperature since 1970, but those have been the exceptions. The most summer warming since that time has come in the Southwest and along the East Coast, which have both warmed as much as 2°-3°F (1°-2°C).

With no change in the rate of greenhouse gas emissions, summers will warm more dramatically in the future. By 2100, the summer climate of Minneapolis could warm by 11°F (6°C), resembling the current summer climate in the northeast Texas town of Mesquite. Seattle would be more like Southern California, and Boston would be more like Miami. The already torrid summers in Phoenix would be more like what is currently seen in Kuwait City in the Middle East.
 


Globally, the complete summer analysis will be not be released by NOAA until Sept. 20, but June and July were the latest in a string of record-hot months. July marked the 15th month in a row of record global heat and was the hottest month in more than a century.

This year is still on track to finish as the hottest year on record. That would make the third record hot year in a row, coming off the back-to-back records of 2014 and 2015.