The Phoenix year in pollen
Pollen seasons in Phoenix: tree pollen February to June, grass April to October, and ragweed from early August until the first frost, around January 3.
First frost lands around January 3 in Phoenix — about 25 days later than Arizona overall — which shifts when ragweed season ends here.
Tree pollen
Grass
Ragweed
When does ragweed season end in Phoenix?
Ragweed season in Phoenix typically ends with the first frost, around January 3. Some years it comes as early as December 30, some as late as January 9.
The rest of the Phoenix pollen year
| Allergen | Typical season |
|---|---|
| Juniper | February to April |
| Mulberry | February to April |
| Ash | February to April |
| Olive | April to May |
| Mesquite | April to June |
| Grass | April to October |
Season-by-season detail is on the Arizona page.
Nearby calendars
Frost dates for Phoenix come from the Phoenix Sky Harbor International Airport weather station's 30-year records. Season windows reviewed August 2026.