Houston Tree & Grass Pollen Count
Measured counts from the Houston Health Department · Thursday, July 23, 2026
Tree pollen is the first big allergy wave of the year in Houston, and grass pollen carries the load through the warm months. The numbers below are actual airborne counts measured at the City of Houston's monitoring station — counted under a microscope, grain by grain — not a forecast. Use them to see exactly what's in the air today and whether levels are climbing or easing.
Grass
MediumLast 60 reporting days
Species breakdown
Grass is reported as a single category total — the Health Department does not break it into individual species.
Trees
NoneLast 60 reporting days
Species breakdown
| Trees | Count |
|---|---|
| Maple (Acer) | 0 |
| Alder (Alnus) | 0 |
| Birch (Betula) | 0 |
| Hickory/Pecan (Carya) | 0 |
| Hackberry (Celtis) | 0 |
| Hazelnut (Corylus) | 0 |
| Cedar (Cupressaceae) | 0 |
| Ash (Fraxinus) | 0 |
| Walnut (Juglans) | 0 |
| Sweet Gum (Liquidambar) | 0 |
| Mulberry (Morus) | 0 |
| Pine (Pinaceae) | 0 |
| Sycamore (Platanus) | 0 |
| Cottonwood (Populus) | 0 |
| Oak (Quercus) | 0 |
| Willow (Salix) | 0 |
| Linden (Tilia) | 0 |
| Elm (Ulmus) | 0 |
| Other Tree | 0 |
Seasonal history — this year vs last
All trends →Daily counts across the calendar year, 2025 vs 2026.
Tree pollen by species
When is tree pollen season in Houston?
Houston's tree pollen season runs roughly from late January through May, with the heaviest stretch in February, March and April. Oak (Quercus) is the dominant offender and the one most likely to coat your car in yellow-green dust; ash, elm, mulberry, pecan and hickory (Carya) add to the spring load, with pecan running a little later into April and May. In winter, mountain cedar (Cupressaceae) blown in from the Texas Hill Country can spike counts on dry, windy December–February days — the cause of the misery many Texans call "cedar fever."
When is grass pollen season in Houston?
Thanks to the Gulf Coast's mild climate, Houston has one of the longest grass pollen seasons in the country — typically March into October, with peaks in late spring and summer. Warm-season grasses like Bermuda, Bahia and Johnson grass are the usual triggers. Because grass pollinates over such a long window, sensitive people often have symptoms for months rather than a few weeks.
How to read the numbers
Counts are reported in grains per cubic meter of air and grouped into None, Low, Medium, Heavy and Extremely heavy. The thresholds differ by pollen type — a "Heavy" tree day is a much bigger number than a "Heavy" grass day — so we color-code each category to its own scale. See theFAQ for the exact cutoffs, or the trends pageto compare this season with prior years.