The Manchester year in pollen
Pollen seasons in Manchester: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around October 19.
First frost lands around October 19 in Manchester — about 16 days later than New Hampshire overall — which shifts when ragweed season ends here.
When does ragweed season end in Manchester?
Ragweed season in Manchester typically ends with the first frost, around October 19. Some years it comes as early as October 13, some as late as October 26.
A light frost around October 19 knocks the season down; the hard freeze that finishes it usually follows by November 1. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Manchester pollen year
| Allergen | Typical season |
|---|---|
| Maple | March to April |
| Birch | April to May |
| Oak | April to June |
| Ash | April to May |
| Pine | May to June |
| Grass | May to July |
Season-by-season detail is on the New Hampshire page.
Nearby calendars
Frost dates for Manchester come from the Manchester Airport weather station's 30-year records. Season windows reviewed August 2026.