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Understanding Annual Pollen Seasons and Weather Trends in the United States

June 17, 2026 · The Clime Team
Understanding Annual Pollen Seasons and Weather Trends in the United States

Pollen seasons in the United States are characterized by three distinct periods: tree pollen in spring, grass pollen in late spring and summer, and weed pollen in late summer and fall. These overlapping seasons span from early February through October, with peak pollen levels varying by region and plant species. (biologyinsights.com)

Spring: Tree Pollen

In early spring, trees such as oak, birch, cedar, and maple release pollen, leading to elevated levels from February through April. In southern states, some trees begin pollinating as early as December or January. (biologyinsights.com)

Late Spring and Summer: Grass Pollen

Grass pollen becomes prominent in late spring and summer, with peak levels from May to July. Common grass species include Bermuda, Timothy, ryegrass, and bluegrass. In cooler regions, grass pollen is most active during late spring and early summer, while in warmer climates, it can be present nearly year-round. (allergyasthmanetwork.org)

Late Summer and Fall: Weed Pollen

Weed pollen, particularly from ragweed, dominates in late summer and fall, with peak levels from August through November. Ragweed pollen can travel hundreds of miles, affecting areas far from its source. (health.clevelandclinic.org)

Impact of Climate Change on Pollen Seasons

Climate change has led to longer and more intense pollen seasons. Studies indicate that the growing season has lengthened by an average of 16 days since 1970, resulting in earlier pollen releases and extended exposure periods. (climatecentral.org) Additionally, higher carbon dioxide levels can increase pollen production, further exacerbating allergy symptoms. (climatecentral.org)

Regional Variations

Pollen seasons vary across the U.S. due to regional climates and plant species. In cooler regions like the Northeast and Midwest, grass pollen peaks from May to July, while in warmer areas such as the Southeast and West Coast, grass pollen can be present nearly year-round. (allergyasthmanetwork.org)

Managing Pollen Exposure

To mitigate pollen exposure:

  • Stay Informed: Monitor local pollen forecasts to anticipate high pollen days.

  • Limit Outdoor Activities: On days with high pollen counts, reduce outdoor activities, especially during peak pollen times.

  • Keep Windows Closed: Use air conditioning to maintain indoor air quality.

  • Shower After Outdoor Exposure: Wash pollen from skin and hair to prevent indoor contamination.

Understanding the timing and intensity of pollen seasons, along with proactive management strategies, can help individuals reduce allergy symptoms and improve quality of life.

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