Climate Central found that the freeze-free fall season has lengthened by an average of 11 days since 1970 in 202 U.S. cities, with 177 seeing later first freezes. The nonprofit says human-caused climate change is extending ragweed’s pollen season.
The five cities with the biggest increases in the freeze-free fall season were Toledo, Ohio (28 days); Reno, Nevada (26); Boise, Idaho, and Tupelo, Mississippi (24 each); and Richmond, Virginia (23). In 67 cities, the season is at least two weeks longer.
Ragweed, found in every state except Alaska, is the main cause of late-summer and fall allergies. About 50 million Americans suffer from fall allergies.
