Frost dates for Mosby 4 ENE, MT
At Mosby 4 ENE, the median last spring frost (32°F) is May 5 and the median first fall frost is Oct 4, for a typical growing season of 151 days. For a 90% chance that the last frost has passed, wait until May 26. Nearby ZIP codes are in USDA hardiness zone 4b.
- May 5Last spring frost (median)50% chance of 32°F after this date
- May 26Safer planting date10% chance of 32°F after this date
- Oct 4First fall frost (median)50% chance of 32°F by this date
- 151 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 4 | May 19 | Jun 4 |
| 32°F | Apr 20 | May 5 | May 26 |
| 28°F | Apr 6 | Apr 20 | May 9 |
| 24°F | Mar 21 | Apr 8 | Apr 26 |
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 14 | Sep 26 | Oct 9 |
| 32°F | Sep 22 | Oct 4 | Oct 19 |
| 28°F | Sep 30 | Oct 14 | Oct 29 |
| 24°F | Oct 5 | Oct 25 | Nov 9 |
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 | 107 days | 128 days | 149 days |
| 32°F | 129 days | 151 days | 173 days |
| 28°F | 151 days | 173 days | 197 days |
| 24°F | 171 days | 196 days | 221 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 |
|---|---|---|---|
| 59058 | 4b | -25 to -20°F | 6 km |
| 59077 | 4b | -25 to -20°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 USC00245872, at 47.0219, -107.8225, elevation 887 m (2,910 ft).
- Data quality: Representative (10+ years), 27 years of freeze data.
- Average days per year at or below 32°F: 159.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Melstone (47 km)
- Flatwillow 4 ENE (47 km)
- Valentine (62 km)
- Ingomar 9 E (70 km)
- Jordan Airport (74 km)
- Grass Range (74 km)
- Jordan (76 km)
- Roundup (84 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.