Allergy Season Lengthens Across the US

Climate change extends pollen-producing season by 21 days on average

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 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

As the climate continues to change, the extended allergy season poses health challenges for those who suffer from seasonal allergies. Longer allergy seasons can lead to increased medication use, doctor visits, and missed work or school days.

The details

The data from Climate Central shows that the length of the allergy season has increased across the country, with some regions seeing even larger increases. This trend is driven by a longer period of time between the last spring freeze and the first fall freeze, allowing plants to grow and release pollen for a longer duration.

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

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 progresses, the lengthening of allergy season is another example of the public health impacts communities will need to address. Individuals may need to take proactive steps like starting allergy medication earlier and being aware of pollen forecasts.