The Indianapolis year in pollen
Pollen seasons in Indianapolis: tree pollen February to May, grass May to July, and ragweed from early August until the first frost, around October 26.
First frost lands around October 26 in Indianapolis — about 5 days later than Indiana overall — which shifts when ragweed season ends here.
When does ragweed season end in Indianapolis?
Ragweed season in Indianapolis typically ends with the first frost, around October 26. Some years it comes as early as October 21, some as late as October 30.
A light frost around October 26 knocks the season down; the hard freeze that finishes it usually follows by November 5. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Indianapolis pollen year
| Allergen | Typical season |
|---|---|
| Oak | April to May |
| Maple | March to April |
| Elm | February to April |
| Birch | April to May |
| Ash | April to May |
| Hickory and walnut | April to May |
| Grass | May to July |
Season-by-season detail is on the Indiana page.
Nearby calendars
Frost dates for Indianapolis come from the Indianapolis weather station's 30-year records. Season windows reviewed August 2026.