The Detroit year in pollen
Pollen seasons in Detroit: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around October 31.
First frost lands around October 31 in Detroit — about 11 days later than Michigan overall — which shifts when ragweed season ends here.
When does ragweed season end in Detroit?
Ragweed season in Detroit typically ends with the first frost, around October 31. Some years it comes as early as October 24, some as late as November 3.
A light frost around October 31 knocks the season down; the hard freeze that finishes it usually follows by November 9. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Detroit pollen year
| Allergen | Typical season |
|---|---|
| Birch | April to May |
| Oak | April to June |
| Maple | March to May |
| Alder | March to April |
| Ash | April to May |
| Pine | May to June |
| Grass | May to July |
Season-by-season detail is on the Michigan page.
Nearby calendars
Frost dates for Detroit come from the Detroit City Airport weather station's 30-year records. Season windows reviewed August 2026.