The Hawaii year in pollen
Tree pollen in Hawaii runs March to October, grass follows January to December, and ragweed starts in early August and fades through December — winters here are usually too mild for the hard stop a frost brings.
When does ragweed season end in Hawaii?
Ragweed season in Hawaii winds down on its own through late December. Most winters never bring the freeze that ends the season elsewhere.
Tree pollen in Hawaii
Tree pollen in Hawaii starts in early March, and kiawe (mesquite) is usually first out. Mild springs pull the start earlier.
| Tree | Typical season | Heaviest weeks |
|---|---|---|
| Kiawe (mesquite) | March to October | early May to late August |
Grass season
Grass pollen in Hawaii runs January to December, heaviest early May to late September. Warm-season grasses like Bermuda do the damage here, and they keep flowering through the heat, which is why the season runs so long. More on grass seasons.
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Common questions
When does ragweed season end in Hawaii?
Ragweed season in Hawaii winds down on its own through late December. Most winters never bring the freeze that ends the season elsewhere.
When does allergy season end in Hawaii?
The last big wave of the Hawaii pollen year is ragweed, so the season ends as ragweed fades out by late December. Tree pollen is done by October, grass mostly by December.
When does tree pollen start in Hawaii?
Tree pollen in Hawaii starts in early March, and kiawe (mesquite) is usually first out. Mild springs pull the start earlier.
Sources: NOAA U.S. Climate Normals (1991–2020 frost records) · Asthma and Allergy Foundation of America — Ragweed Pollen. Season windows reviewed August 2026.