Ragweed season in Hawaii fades out rather than ending
Everywhere else in the country, ragweed season has a hard stop: the first freeze kills the plants and the pollen quits. Hawaii doesn't reliably get one, so the season tapers instead — thinning out through late December rather than ending on a date.
Is ragweed season still going in Hawaii?
- Ragweed In season now — about 4 months before it fades out
Status comes from the typical season window for this area, not from a pollen count — a cool spring or a late frost moves the real dates by a week or two either way. These are the windows for Hawaii.
Why there's no end date here
Hawaii has no first-frost date to look up. Everywhere else, the end of ragweed season is a freeze: NOAA records the first 32°F frost that ends it and the first 28°F hard freeze that follows. Here those nights don't reliably come, so nothing cuts the season off — the plants finish their one-year cycle and die back on their own schedule.
Many people plan ahead of the season; if that includes anything medical, ask your doctor.
What comes after
With no freeze to draw the line, the Hawaii ragweed year simply runs out rather than stopping — and tree pollen opens the next one in early March.
The full Hawaii pollen year — tree, grass and ragweed, with the dates each one starts — is on the Hawaii season page. For how ragweed works nationally, see ragweed season.
Common questions
When does ragweed season end in Hawaii?
It doesn't end on a date. Hawaii rarely freezes hard enough to kill the plants, so ragweed thins out through late December and is gone by winter without a clear last day.
Why doesn't frost end it in Hawaii?
Because it effectively never comes. Common ragweed is an annual with no defense against a freeze, so almost everywhere in the country one cold night kills the plants and the pollen stops within the week. Hawaii doesn't get those nights at the elevations people live at, so the season has to end the slow way instead.
What comes after ragweed in Hawaii?
Nothing, for a while — ragweed is the last pollen of the year. The next season to open in Hawaii is tree pollen in early March, usually starting with kiawe (mesquite).
Sources: NOAA U.S. Climate Normals, 1991–2020 (first-frost and hard-freeze dates) · Asthma and Allergy Foundation of America · Iowa State University Extension — common ragweed. Season windows reviewed August 2026.