Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 59802
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 59802 in zone 5b (the coldest night of a typical year: -15 to -10°F).
The nearest station, Missoula (2 mi NE), MT, is 2 miles from the ZIP's center: its last spring frost comes after May 10 in half of years and after May 28 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Missoula (2 mi NE), MT | 2 mi | 3,420 ft | May 10 | May 28 | October 1 | – |
| Missoula 6 NW Weather Office, MT | 8 mi | 3,197 ft | May 6 | May 19 | October 4 | – |
| Missoula, MTMissoula International Airport | 8 mi | 3,192 ft | May 16 | June 1 | September 26 | 5b |
| Alberton, MT | 27 mi | 3,060 ft | May 18 | June 6 | September 25 | 6a |
| Stevensville, MT | 28 mi | 3,375 ft | May 22 | June 13 | September 19 | 5b |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at Missoula (2 mi NE)
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | June 24 | June 10 | June 1 | May 12 | September 19 | September 3 |
| 32°F | May 28 | May 17 | May 10 | April 27 | October 1 | September 16 |
| 28°F (hard freeze) | May 11 | May 3 | April 28 | April 12 | October 12 | September 28 |
| 24°F | April 28 | April 17 | April 8 | March 19 | October 24 | October 7 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.