The Hilo year in pollen
Pollen seasons in Hilo: tree pollen March to October, grass January to December, and ragweed from early August, fading out by late December.
Tree pollen
Grass
Ragweed
When does ragweed season end in Hilo?
Ragweed around Hilo winds down on its own through late December — most winters never bring a season-ending freeze.
The rest of the Hilo pollen year
| Allergen | Typical season |
|---|---|
| Kiawe (mesquite) | March to October |
| Grass | January to December |
Season-by-season detail is on the Hawaii page.
Nearby calendars
Frost dates for Hilo come from the Hilo International Airport weather station's 30-year records. Season windows reviewed August 2026.