About PollenDates

PollenDates answers one question: when do pollen seasons start and end where you live? Tree pollen, grass, and ragweed each get a calendar window for every state and more than 200 cities — when the season typically begins, when it peaks, and when it's over.

The ragweed dates lean on a simple piece of natural timing: ragweed keeps making pollen until the first frost kills it. So "when does ragweed season end" is really "when does frost usually arrive" — and that question has a solid answer. We use typical first-frost dates from NOAA's 30-year climate records (1991-2020), weather station by weather station.

Tree and grass windows come from university extension and aerobiology research — the people who count pollen for a living. Every window is typical, not a forecast: a mild spring runs early, a warm fall runs late. Season windows were last reviewed August 2026; frost records were last refreshed August 15, 2026.

PollenDates doesn't cover symptoms or treatment — that's between you and your doctor. We do dates.