Grass season: one wave up north, a long haul down south
Grass is the summer allergen, but "summer" means very different things depending on which grasses grow where you live. The dividing line runs roughly through the middle of the country.
Typical windows by region
| Region | Grass season | Grasses | States |
|---|---|---|---|
| Northeast | May to July | cool-season (timothy, bluegrass) | CT , ME , MA , NH , NJ , NY , PA , RI , VT |
| Mid-Atlantic | May to July | cool-season (timothy, bluegrass) | DE , DC , MD , VA , WV |
| Southeast | April to September | both, in sequence | AL , GA , KY , NC , SC , TN |
| Florida | March to October | warm-season (Bermuda and kin) | FL |
| Gulf South | April to September | warm-season (Bermuda and kin) | AR , LA , MS |
| Midwest | May to July | cool-season (timothy, bluegrass) | IL , IN , IA , MO , OH |
| Upper Midwest | May to July | cool-season (timothy, bluegrass) | MI , MN , WI |
| Plains | May to August | both, in sequence | KS , NE , ND , OK , SD |
| Texas | March to October | warm-season (Bermuda and kin) | TX |
| Desert Southwest | April to October | warm-season (Bermuda and kin) | AZ , NV , NM |
| Mountain West | May to July | cool-season (timothy, bluegrass) | CO , ID , MT , UT , WY |
| Pacific Northwest | May to July | cool-season (timothy, bluegrass) | OR , WA |
| California | March to July | both, in sequence | CA |
| Alaska | June to August | cool-season (timothy, bluegrass) | AK |
| Hawai'i | January to December | warm-season (Bermuda and kin) | HI |
Common questions
When is grass pollen season?
Across the northern half of the country, grass season is a single wave from roughly mid-May to mid-July, peaking in June. Across the South, warm-season grasses like Bermuda keep flowering from spring into September.
Why is the season so much longer in the South?
It's a different cast of grasses. Northern lawns and meadows are cool-season species — timothy, bluegrass, orchard grass — which flower once in early summer and quit. Southern lawns are warm-season species that flower as long as the heat lasts.
Season windows come from university extension turf and aerobiology research, reviewed August 2026. State pages carry their sources.