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Fall Temperature Trends

If you live in the Northeast or Midwest, you’ve already gotten a taste of fall weather (despite this late season round of heat). But now that meteorological autumn is officially here, it’s time to look at how the climate of fall has been changing over the past four decades or so.

The world as a whole has warmed over that time, as the planet’s blanket of heat-trapping CO2 and other greenhouse gases has gotten progressively thicker. However, more storylines emerge when you break down the warming by specific seasons and regions. 

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Overall, fall across the U.S. has been warming by 0.46°F per decade since 1970. That warming, of course, comes with its regional variations. West of the Mississippi, there’s been an unmistakable warming trend with average fall temperature rising by up to 1.2°F per decade in some areas. It’s also been warming in the Northeast, but fall in the Southeast has featured relatively little change in temperature over the past 40 years. The so-called “warming hole” features pockets where fall average temperatures have dropped slightly. Now that doesn't mean warming is sparing the region. Annual temperatures trends show that all states in the Southeast (and across the U.S. for that matter) have been warming since 1970.

Looking to the future, fall is likely to only get hotter for everyone with the Southwest leading the way. According to the National Climate Assessment, temperatures in the region will rise 5°F to 9°F by the end of the century with the steepest increases coming in fall and summer. This warming could lead to a range of impacts nationwide, such as pushing back the fall harvest, delaying the frost/freeze season (which plays into the life cycles of species and ecosystems), extending the wildfire season, and affecting fall foliage displays.