The San Jose year in pollen
Pollen seasons in San Jose: tree pollen January to June, grass March to July, and ragweed from early August until the first frost, around December 22.
First frost lands around December 22 in San Jose — about 7 days later than California overall — which shifts when ragweed season ends here.
When does ragweed season end in San Jose?
Ragweed season in San Jose typically ends with the first frost, around December 22. Some years it comes as early as December 12, some as late as January 1.
A light frost around December 22 knocks the season down; the hard freeze that finishes it usually follows by December 28. Based on 30 years of NOAA frost records (1991–2020).
The rest of the San Jose 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 San Jose come from the San Jose weather station's 30-year records. Season windows reviewed August 2026.