The Oklahoma year in pollen
Tree pollen in Oklahoma runs February to May, grass follows May to August, and ragweed starts in early August and holds on until the first frost — typically around November 4.
When does ragweed season end in Oklahoma?
Ragweed season in Oklahoma typically ends with the first frost, around November 4.
Ragweed keeps releasing pollen until a freeze kills the plants, which is why the season has no fixed end date — it ends when the cold arrives. More on how frost ends ragweed season.
Tree pollen in Oklahoma
Tree pollen in Oklahoma starts in mid-February, and eastern red cedar is usually first out. Mild springs pull the start earlier.
| Tree | Typical season | Heaviest weeks |
|---|---|---|
| Eastern red cedar | February to April | early March to early April |
| Elm | February to April | — |
| Maple | March to April | — |
| Oak | April to May | mid-April to early May |
| Cottonwood | April to May | — |
Grass season
Grass pollen in Oklahoma runs May to August, heaviest mid-May to early July. Cool-season grasses flower in the first wave; warm-season grasses like Bermuda pick up through summer, which stretches the season. More on grass seasons.
First frost — and ragweed's end — city by city
The first frost sweeps across Oklahoma over several weeks, and ragweed season ends with it. Based on 30 years of NOAA frost records (1991–2020).
| City | Typical first frost |
|---|---|
| Lawton | November 5 |
| Oklahoma City | November 2 |
| Tulsa | November 4 |
Common questions
When does ragweed season end in Oklahoma?
Ragweed season in Oklahoma typically ends with the first frost, around November 4.
When does allergy season end in Oklahoma?
The last big wave of the Oklahoma pollen year is ragweed, so the season ends with the first frost, around November 4. Tree pollen is done by May, grass mostly by August.
When does tree pollen start in Oklahoma?
Tree pollen in Oklahoma starts in mid-February, and eastern red cedar is usually first out. Mild springs pull the start earlier.
Sources: NOAA U.S. Climate Normals (1991–2020 frost records) · Asthma and Allergy Foundation of America — Ragweed Pollen. Season windows reviewed August 2026.