Frost dates for Miles City F Wiley Field, MT
At Miles City F Wiley Field, the median last spring frost (32°F) is May 8 and the median first fall frost is Sep 30, for a typical growing season of 144 days. For a 90% chance that the last frost has passed, wait until May 21. Nearby ZIP codes are in USDA hardiness zones 4a to 4b.
- May 8Last spring frost (median)50% chance of 32°F after this date
- May 21Safer planting date10% chance of 32°F after this date
- Sep 30First fall frost (median)50% chance of 32°F by this date
- 144 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 |
|---|---|---|---|
| 36°F | May 7 | May 18 | May 31 |
| 32°F | Apr 26 | May 8 | May 21 |
| 28°F | Apr 13 | Apr 29 | May 12 |
| 24°F | Apr 2 | Apr 17 | May 3 |
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 |
|---|---|---|---|
| 36°F | Sep 10 | Sep 23 | Oct 4 |
| 32°F | Sep 17 | Sep 30 | Oct 14 |
| 28°F | Sep 25 | Oct 8 | Oct 23 |
| 24°F | Oct 1 | Oct 18 | Oct 31 |
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 | 106 days | 124 days | 143 days |
| 32°F | 126 days | 144 days | 162 days |
| 28°F | 143 days | 163 days | 183 days |
| 24°F | 161 days | 183 days | 204 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 59301 | 4b | -25 to -20°F | 7 km |
| 59333 | 4a | -30 to -25°F | 29 km |
| 59338 | 4a | -30 to -25°F | 30 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 USW00024037, at 46.4267, -105.8825, elevation 800 m (2,624 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 166.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Mizpah 4 NNW (48 km)
- Rock Springs (52 km)
- Terry (60 km)
- Forsyth (63 km)
- Brandenberg (73 km)
- Terry 21 NNW (77 km)
- Mildred 5 N (80 km)
- Colstrip (83 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.