The Indiana year in pollen

When does ragweed season end in Indiana?

Ragweed season in Indiana typically ends with the first frost, around October 21. The coldest corners of the state see frost by mid-October; the mildest hold out until late October.

Ragweed keeps releasing pollen until a freeze kills the plants, which is why the season has no fixed end date — it ends when the cold arrives. More on how frost ends ragweed season.

Tree pollen in Indiana

Tree pollen in Indiana starts in mid-February, and elm is usually first out. Oak — the bigger problem for most people — follows April to May. Mild springs pull the start earlier.

Grass season

Grass pollen in Indiana runs May to July, heaviest late May to late June. The culprits are cool-season lawn and meadow grasses — timothy, bluegrass, orchard grass — which flower in one early-summer wave. More on grass seasons.

First frost — and ragweed's end — city by city

The first frost sweeps across Indiana over several weeks, and ragweed season ends with it. Based on 30 years of NOAA frost records (1991–2020).

Common questions

When does ragweed season end in Indiana?

Ragweed season in Indiana typically ends with the first frost, around October 21. The coldest corners of the state see frost by mid-October; the mildest hold out until late October.

When does allergy season end in Indiana?

The last big wave of the Indiana pollen year is ragweed, so the season ends with the first frost, around October 21. Tree pollen is done by May, grass mostly by July.

When does tree pollen start in Indiana?

Tree pollen in Indiana starts in mid-February, and elm is usually first out. Oak — the bigger problem for most people — follows April to May. Mild springs pull the start earlier.