The Nevada year in pollen
Tree pollen in Nevada runs February to June, grass follows April to October, and ragweed starts in early August and holds on until the first frost — typically around October 23.
When does ragweed season end in Nevada?
Ragweed season in Nevada typically ends with the first frost, around October 23. The coldest corners of the state see frost by mid-September; the mildest hold out until early December.
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 Nevada
Tree pollen in Nevada starts in early February, and juniper is usually first out. Mild springs pull the start earlier.
| Tree | Typical season | Heaviest weeks |
|---|---|---|
| Juniper | February to April | mid-February to late March |
| Mulberry | February to April | early March to early April |
| Ash | February to April | — |
| Olive | April to May | mid-April to mid-May |
| Mesquite | April to June | — |
Grass season
Grass pollen in Nevada runs April to October, heaviest early May to late June. 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.
First frost — and ragweed's end — city by city
The first frost sweeps across Nevada over several weeks, and ragweed season ends with it. Based on 30 years of NOAA frost records (1991–2020).
| City | Typical first frost |
|---|---|
| Elko | September 18 |
| Las Vegas | December 10 |
| Reno | October 23 |
Common questions
When does ragweed season end in Nevada?
Ragweed season in Nevada typically ends with the first frost, around October 23. The coldest corners of the state see frost by mid-September; the mildest hold out until early December.
When does allergy season end in Nevada?
The last big wave of the Nevada pollen year is ragweed, so the season ends with the first frost, around October 23. Tree pollen is done by June, grass mostly by October.
When does tree pollen start in Nevada?
Tree pollen in Nevada starts in early February, and juniper 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.