The Fresno year in pollen
Pollen seasons in Fresno: tree pollen January to June, grass March to July, and ragweed from early August until the first frost, around December 14.
Tree pollen
Grass
Ragweed
When does ragweed season end in Fresno?
Ragweed season in Fresno typically ends with the first frost, around December 14. Some years it comes as early as December 6, some as late as December 28.
A light frost around December 14 knocks the season down; the hard freeze that finishes it usually follows by December 24. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Fresno pollen year
| Allergen | Typical season |
|---|---|
| Oak | March to May |
| Cypress and juniper | January to March |
| Alder | January to March |
| Olive | April to June |
| Walnut | April to May |
| Grass | March to July |
Season-by-season detail is on the California page.
Nearby calendars
Frost dates for Fresno come from the Fresno Yosemite International Airport weather station's 30-year records. Season windows reviewed August 2026.