Updated June 2026
Ragweed Pollen Guide (1970)
Ragweed (Ambrosia) pollen drives late-summer and fall allergies across most of North America. Real microscope counts, season timing, and relief.
When is ragweed season?
Ragweed (Ambrosia artemisiifolia and A. trifida) typically releases pollen from mid-August through the first hard frost, peaking in early-to-mid September across most of the United States.
Why ragweed pollen counts matter
A single ragweed plant can release a billion pollen grains in a season. Grains are small (~20µm) and wind-carried for hundreds of miles, which is why ragweed is the dominant fall allergen even in cities far from cultivated land.
Real PollyMap microscope data
The card above shows current ragweed activity in your area, computed from approved partner microscope samples over the last 7 days.