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 59722
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 59722 in zone 4b (the coldest night of a typical year: -25 to -20°F).
The nearest station, Anaconda, MT, is 18 miles from the ZIP's center: its last spring frost comes after June 1 in half of years and after June 25 in one year in ten. By the USDA's method its plant hardiness zone is 5a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Anaconda, MT | 18 mi | 5,230 ft | June 1 | June 25 | September 14 | 5a |
| Elliston, MT | 21 mi | 5,080 ft | June 9 | June 26 | September 8 | – |
| Butte, MTButte Bert Mooney Airport | 29 mi | 5,506 ft | June 13 | July 1 | September 5 | 4a |
| Austin (1 mi W), MT | 31 mi | 4,851 ft | June 4 | June 18 | September 14 | – |
| Boulder, MT | 32 mi | 4,904 ft | June 7 | June 25 | September 8 | 4b |
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 Anaconda
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% |
|---|---|---|---|---|---|---|
| 32°F | June 25 | June 11 | June 1 | May 14 | September 14 | August 31 |
| 28°F (hard freeze) | May 30 | May 19 | May 13 | April 29 | September 28 | September 12 |
| 24°F | May 13 | May 6 | May 1 | April 17 | October 7 | September 23 |
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.