The Wilmington year in pollen
Pollen seasons in Wilmington: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around November 1.
First frost lands around November 1 in Wilmington — about 9 days later than Delaware overall — which shifts when ragweed season ends here.
When does ragweed season end in Wilmington?
Ragweed season in Wilmington typically ends with the first frost, around November 1. Some years it comes as early as October 28, some as late as November 7.
A light frost around November 1 knocks the season down; the hard freeze that finishes it usually follows by November 14. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Wilmington pollen year
| Allergen | Typical season |
|---|---|
| Oak | March to May |
| Maple | March to April |
| Birch | March to May |
| Ash | March to April |
| Pine | April to June |
| Grass | May to July |
Season-by-season detail is on the Delaware page.
Nearby calendars
Frost dates for Wilmington come from the Wilmington New Castle Co Airport weather station's 30-year records. Season windows reviewed August 2026.