Allergy Season Lengthens Across U.S. Due to Climate Change

Climate Central data shows allergy season has grown 21 days longer on average since the 1970s.

Published on Mar. 6, 2026

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New data from Climate Central reveals that allergy season has grown significantly longer across the United States over the past several decades. On average, the allergy season has expanded by 21 extra 'freeze-free' days since the 1970s, giving plants more time to grow and release pollen that triggers allergic reactions in 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 and pollinate 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

Climate Central's analysis found that allergy season has grown longer in every part of the country, with some regions seeing increases of over a month. The extra days of pollen production can exacerbate symptoms for those with allergies, leading to more missed work and school days, increased use of medication, and a general decrease in overall wellbeing.

  • Since the 1970s, allergy season has expanded by an average of 21 extra 'freeze-free' days across the United States.

The players

Climate Central

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

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The takeaway

The lengthening of allergy season is a clear sign of the impacts of climate change, and serves as a warning that the effects will continue to worsen unless significant action is taken to reduce greenhouse gas emissions and mitigate global warming.