Allergy Season Lengthens Across US

Climate change extends pollen season by 3 weeks on average

Published on Mar. 6, 2026

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New data from Climate Central shows that allergy season has grown significantly longer across the United States since the 1970s, with the average freeze-free period increasing by 21 days. This gives plants more time to grow and release pollen, exacerbating seasonal allergies for millions of Americans.

Why it matters

Longer allergy seasons driven by climate change can have serious health impacts, leading to more severe and prolonged allergy symptoms for those with sensitivities. This trend also highlights the need for better allergy management strategies and potential agricultural adaptations to mitigate the effects of a warming climate.

The details

The Climate Central analysis found that the length of the freeze-free period has increased by an average of 21 days across the country since the 1970s. This extended growing season allows plants to produce and release pollen for a longer duration each year, intensifying allergy symptoms for those affected.

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

The players

Climate Central

A non-profit research and journalism organization that analyzes and reports on the science and impacts of climate change.

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The takeaway

As the climate continues to warm, allergy sufferers can expect their symptoms to worsen and last longer each year. This underscores the need for improved allergy management strategies and agricultural adaptations to address the public health challenges posed by a lengthening allergy season.