Ragweed Season in Houston
Measured counts from the Houston Health Department · Thursday, July 23, 2026
Ragweed (Ambrosia) is the single biggest cause of fall allergies in Houston. If you feel great all summer and then hit a wall of sneezing and congestion in late August, ragweed is almost certainly why. The count above is the Health Department's measured weed pollen for today — not a forecast.
When does ragweed season start and end in Houston?
In Houston, ragweed typically starts in mid-to-late August, peaks in September and October, and winds down through November, usually ending after the first hard cold front. Houston's mild autumn gives ragweed a longer run than it gets in northern states, where an early freeze cuts it short.
Why ragweed affects so many people
A single ragweed plant can produce up to a billion pollen grains in one season, and those grains are light enough to drift for hundreds of miles on the wind. That's why you can have severe symptoms even with no ragweed growing near you. Ragweed pollen also cross-reacts with some foods (like melon and banana) for certain people, a phenomenon called oral allergy syndrome.
Other fall weeds in the count
Ragweed overlaps with several other weeds the Health Department tracks in late summer and fall, including pigweed and amaranth, sage and mugwort (Artemisia), and sedge. See the fullweed pollen page for today's species breakdown, and thetrends page to watch the fall ramp-up year over year.
Getting ahead of it
Because ragweed season is so predictable, many people start preventive allergy treatment a couple of weeks before it usually begins. Track the daily weed count here so you know when levels are actually climbing, and see the FAQ for exposure tips. For a treatment plan, talk to a board-certified allergist — this page is informational, not medical advice.