Frost dates for Choteau, MT
At Choteau, the median last spring frost (32°F) is May 28 and the median first fall frost is Sep 12, for a typical growing season of 104 days. For a 90% chance that the last frost has passed, wait until Jun 20. Nearby ZIP codes are in USDA hardiness zones 4a to 4b.
- May 28Last spring frost (median)50% chance of 32°F after this date
- Jun 20Safer planting date10% chance of 32°F after this date
- Sep 12First fall frost (median)50% chance of 32°F by this date
- 104 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 32°F | May 15 | May 28 | Jun 20 |
| 28°F | May 1 | May 14 | May 27 |
| 24°F | Apr 15 | Apr 30 | May 14 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 32°F | Aug 30 | Sep 12 | Sep 27 |
| 28°F | Sep 9 | Sep 25 | Oct 7 |
| 24°F | Sep 24 | Oct 5 | Oct 21 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 43 days | 69 days | 92 days |
| 32°F | 78 days | 104 days | 124 days |
| 28°F | 112 days | 134 days | 151 days |
| 24°F | 138 days | 157 days | 177 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 59419 | 4b | -25 to -20°F | 19 km |
| 59422 | 4b | -25 to -20°F | 22 km |
| 59436 | 4b | -25 to -20°F | 23 km |
| 59467 | 4b | -25 to -20°F | 32 km |
| 59433 | 4a | -30 to -25°F | 38 km |
| 59443 | 4b | -25 to -20°F | 39 km |
| 59468 | 4b | -25 to -20°F | 43 km |
| 59477 | 4b | -25 to -20°F | 45 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00241737, at 47.8206, -112.1922, elevation 1172 m (3,845 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 177.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Choteau 8ne (14 km)
- Bynum 4 SSE (14 km)
- Fairfield (28 km)
- Blackleaf (28 km)
- Augusta (40 km)
- Conrad (43 km)
- Gibson Dam (49 km)
- Sun River 4 S (51 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.