Allergy Season Lengthens Across US, Data Shows

Climate Central reports longer 'freeze-free' periods allow plants more time to grow and release pollen.

Published on Mar. 6, 2026

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According to newly released data from Climate Central, 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 concerning trend driven by climate change, as it means more people will suffer from allergies for a greater portion of the year. This has implications for public health, productivity, and quality of life for those affected.

The details

The data from Climate Central shows that the seasonal part of 'seasonal allergies' is becoming less seasonal, with allergy season starting earlier and lasting longer across the country. This is due to the increase in 'freeze-free' days, which allows plants to grow and release pollen for a longer period of time each year.

  • 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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What’s next

Climate Central plans to continue monitoring changes in allergy season length and severity as the climate continues to warm.

The takeaway

The lengthening of allergy season is a clear sign of the impacts of climate change, and highlights the need for greater awareness and action to address this growing public health issue.