Houston Weed Pollen & Ragweed Count
Measured counts from the Houston Health Department · Thursday, July 23, 2026
If your allergies flare up in late summer and fall, weed pollen — and ragweed above all — is the most likely culprit in Houston. The count below is the actual amount measured in the air today, not a forecast, with a breakdown of exactly which weeds are pollinating.
Weeds
MediumLast 60 reporting days
Species breakdown
| Weeds | Count |
|---|---|
| Other Weed | 30 |
| Sedge (Cyperaceae) | 4 |
| Plantain (Plantago) | 4 |
| Cattail (Typha) | 4 |
| Amaranth (Chenopodiaceae/ Amaranthaceae) | 2 |
| Ragweed (Ambrosia) | 0 |
| Sage (Artemisia) | 0 |
| Aster (Asteraceae) | 0 |
| Sheep Sorel (Rumex) | 0 |
| Nettle (Urticaceae) | 0 |
Seasonal history — this year vs last
All trends →Daily counts across the calendar year, 2025 vs 2026.
Weed pollen by species
When is ragweed season in Houston?
Ragweed (Ambrosia) season in Houston typically runs from mid-August through November, peaking in September and October before the first real cold front knocks it down. A single ragweed plant can release a billion pollen grains in a season, and those grains are light enough to travel for miles — which is why you can react even with no ragweed in your own yard. It's the leading cause of fall hay fever nationwide, and Houston's long, warm autumn gives it plenty of runway.
Other Houston weeds that trigger allergies
Ragweed gets the headlines, but the Health Department also tracks pigweed and amaranth (Chenopodiaceae/Amaranthaceae), sage and mugwort (Artemisia),sedge (Cyperaceae), plantain (Plantago) and nettle (Urticaceae). Many of these overlap with ragweed in late summer and fall, so the "weed" total can stay elevated for months along the Gulf Coast.
How to read the numbers
Weed pollen is reported in grains per cubic meter and graded None, Low, Medium, Heavy or Extremely heavy on a scale specific to weeds. See the FAQ for the exact thresholds, the ragweed season guide for what to expect month by month, or the trends page to compare this fall with prior years.