The Missouri year in pollen
Tree pollen in Missouri runs February to May, grass follows May to July, and ragweed starts in early August and holds on until the first frost — typically around October 29.
When does ragweed season end in Missouri?
Ragweed season in Missouri typically ends with the first frost, around October 29.
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 Missouri
Tree pollen in Missouri starts in mid-February, and elm is usually first out. Oak — the bigger problem for most people — follows April to May. Mild springs pull the start earlier.
| Tree | Typical season | Heaviest weeks |
|---|---|---|
| Oak | April to May | mid-April to mid-May |
| Maple | March to April | mid-March to early April |
| Elm | February to April | — |
| Birch | April to May | — |
| Ash | April to May | — |
| Hickory and walnut | April to May | — |
Grass season
Grass pollen in Missouri runs May to July, heaviest late May to late June. The culprits are cool-season lawn and meadow grasses — timothy, bluegrass, orchard grass — which flower in one early-summer wave. More on grass seasons.
First frost — and ragweed's end — city by city
The first frost sweeps across Missouri over several weeks, and ragweed season ends with it. Based on 30 years of NOAA frost records (1991–2020).
| City | Typical first frost |
|---|---|
| Columbia | October 29 |
| Kansas City | November 2 |
| Springfield | October 27 |
| St. Louis | November 4 |
Common questions
When does ragweed season end in Missouri?
Ragweed season in Missouri typically ends with the first frost, around October 29.
When does allergy season end in Missouri?
The last big wave of the Missouri pollen year is ragweed, so the season ends with the first frost, around October 29. Tree pollen is done by May, grass mostly by July.
When does tree pollen start in Missouri?
Tree pollen in Missouri starts in mid-February, and elm is usually first out. Oak — the bigger problem for most people — follows April to May. 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.