Warmer Fall Extends Allergy Season Across U.S.
Warmer Fall Extends Allergy Season Across U.S.
US · Published Sep 23, 2026
• A warming climate is extending the freeze-free growing season across the United States, leading to longer allergy seasons. According to Climate Central, the average freeze-free fall season has lengthened by 11 days in 88% of 202 analyzed U.S. cities since
• This trend is particularly concerning for the 50 million Americans who suffer from ragweed allergies, as the plant thrives in warmer conditions and produces significant amounts of pollen. The Northwest region has experienced the most significant increase, with an average of 14 additional freeze-free days. The extended growing season allows ragweed and other allergenic plants to release pollen for longer periods, exacerbating allergy symptoms for many individuals. This phenomenon is linked to heat-trapping pollution and increased atmospheric carbon dioxide levels, which further boost pollen production.

Impact & Risks

The extended allergy season poses health risks for millions of Americans, particularly those with ragweed allergies or asthma. Prolonged exposure to pollen can lead to more severe allergy symptoms, including sneezing, congestion, and respiratory issues. Urban areas may face heightened risks due to the urban heat island effect, which accelerates ragweed growth and pollen production. Additionally, mold spores, which peak in late summer and fall, can exacerbate allergies and asthma. The combination of longer pollen seasons and increased mold activity could lead to a rise in allergy-related health issues, particularly in regions experiencing the most significant warming trends.

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