Allergy Season Lengthens Across the U.S.

Climate change extends pollen season by 21 days on average since the 1970s.

Published on Mar. 6, 2026

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New data from Climate Central shows that allergy season has grown longer in every part of the United States, by an average of 21 extra 'freeze-free' days since the 1970s. 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 freezing days allow plants to bloom for a longer period each year. This trend is impacting the health and quality of life for millions of Americans who suffer from seasonal allergies.

The details

The Climate Central analysis found that the allergy season has expanded by an average of 21 days across the country, with some regions seeing even larger increases. This extended growing season gives plants more time to produce and release pollen, exacerbating symptoms for those with allergies.

  • The data analyzed changes in allergy season since the 1970s.

The players

Climate Central

A non-profit science and news organization that analyzes and reports on climate change.

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The takeaway

As climate change continues to impact the environment, the growing season for plants is expanding, leading to longer and more severe allergy seasons for millions of Americans. This trend highlights the need to address the root causes of climate change to mitigate its effects on public health.