Allergy Season Grows Longer Across the US

Climate data shows allergy season has expanded by an average of 21 days since the 1970s.

Published on Mar. 6, 2026

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Newly released 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 can trigger allergic reactions in many people.

Why it matters

Longer allergy seasons can have significant impacts on public health, leading to increased suffering and medical costs for those with seasonal allergies. This trend is likely driven by climate change, as warmer temperatures and shifting precipitation patterns allow plants to bloom for a greater portion of the year.

The details

The data from Climate Central shows that allergy season has grown longer in every part of the country, with some regions seeing even more dramatic expansions. This gives plants more time to grow and release pollen, exacerbating allergy symptoms for millions of Americans.

  • The data analyzed changes in allergy season length 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

This trend of longer allergy seasons is a clear sign of the impacts of climate change, and highlights the need for continued research and public awareness around this growing public health issue.