Allergy Season Lengthens Across US

Climate change extends pollen season by 3 weeks on average

Published on Mar. 4, 2026

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New data from Climate Central shows that allergy season has grown longer in every part of the United States since the 1970s, by an average of 21 extra 'freeze-free' days. This gives plants more time to grow and release the pollen that causes seasonal allergies for many people.

Why it matters

The lengthening of allergy season is a direct result of climate change, as warmer temperatures and fewer freezes allow plants to bloom and release pollen for a longer period each year. This can exacerbate respiratory issues and reduce quality of life for those who suffer from seasonal allergies.

The details

The analysis by Climate Central found that allergy season has expanded by an average of 21 days across the country since the 1970s. Some regions have seen even more dramatic increases, with parts of the Southwest and Northeast experiencing over 30 additional days of pollen production annually.

  • The analysis looked at data from the 1970s to the present day.

The players

Climate Central

A nonprofit science and news organization that analyzes and reports on the changing climate and its impact on the public.

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The takeaway

As climate change continues to alter weather patterns, the growing season for plants that trigger seasonal allergies is expanding, causing increased suffering for allergy sufferers. This trend underscores the need to address the root causes of climate change to mitigate its public health impacts.