The hottest cities are pretty much where you would expect them to be, all located in southern states, like Florida, Texas and Arizona. And these top 25 cities all either have blistering summer heat - McAllen, Texas, for example, averages 87°F in July and August - or are just generally hot year-round, as is the case in Miami.
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Conversely, the fastest-warming cities aren't clustered in any one region. In fact, the top 25 fastest-warming cities are scattered over 16 states. Some of these rapidly warming cities are traditional hotspots, like Phoenix and Las Vegas. But many are not places you would consider to be hot, like Fargo, N.D., or Minneapolis.
To find the hottest cities, we looked at the top 200 largest metro areas in the United States and calculated their average annual temperature from 1981-2010. To figure out which of those 200 cities have been warming the fastest, we calculated how average annual temperatures have been changing since 1965.
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Of the 178 cities with sufficient data for our analysis, all but three have seen their average temperatures warm overall in the past 50 years. The top 25 cities have all seen temperatures climb by more than 0.6°F per decade - that's at least 3°F hotter over 50 years.
The regional distribution of the fastest-warming cities shows how temperature trends can vary from place to place. Nationwide, annual temperatures have been rising over the past 50 years, consistent with global warming caused by increasing greenhouse gas emissions. Drilling down to the city level, these rising temperatures are also consistent with the broader warming trend, though urban heat islands may also be contributing to some local warming.
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