Warming climate prompts longer allergy season in Portland
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Grab your tissues: Allergy season is getting longer in Portland amid climate change, according to a new analysis from Climate Central.
The big picture: The freeze-free growing season for plants lengthened from 1970 to 2025 in nearly 90% of the 198 cities analyzed in the climate research group's latest report.
- Among cities with an increase, the freeze-free period lengthened by an average of 21 days.
- That's the time between the last and first freeze, used here to represent allergy season.
Zoom in: Allergy season has lengthened the most in the Northwest, where the freeze-free period is now 30 days longer in Portland and 41 days longer in Eugene.
What they're saying: "As temperatures rise, freeze-free seasons are stretching in every region of the country, giving plants weeks of extra time to grow and release pollen," Climate Central's Kristy Dahl said in a statement.
- "For millions of Americans, that means earlier, longer, and often more intense allergy seasons that can take a real toll on health and daily life."