Frost dates for Opheim 10 N, MT
At Opheim 10 N, the median last spring frost (32°F) is Jun 1 and the median first fall frost is Sep 7, for a typical growing season of 99 days. For a 90% chance that the last frost has passed, wait until Jun 18. Nearby ZIP codes are in USDA hardiness zone 3b.
- Jun 1Last spring frost (median)50% chance of 32°F after this date
- Jun 18Safer planting date10% chance of 32°F after this date
- Sep 7First fall frost (median)50% chance of 32°F by this date
- 99 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 20 | Jun 1 | Jun 18 |
| 28°F | May 9 | May 21 | Jun 4 |
| 24°F | Apr 28 | May 12 | May 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 |
|---|---|---|---|
| 32°F | Aug 24 | Sep 7 | Sep 21 |
| 28°F | Sep 5 | Sep 19 | Oct 1 |
| 24°F | Sep 13 | Sep 28 | Oct 11 |
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 | 39 days | 65 days | 91 days |
| 32°F | 73 days | 99 days | 117 days |
| 28°F | 100 days | 119 days | 137 days |
| 24°F | 117 days | 137 days | 157 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 |
|---|---|---|---|
| 59250 | 3b | -35 to -30°F | 25 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 USC00246236, at 48.9989, -106.3800, elevation 877 m (2,878 ft).
- Data quality: Representative (10+ years), 28 years of freeze data.
- Average days per year at or below 32°F: 210.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Opheim 12 SSE (34 km)
- St. Marie (66 km)
- Scobey 4 NW (69 km)
- Glasgow Intl Airport (89 km)
- Glasgow #2 (92 km)
- Hinsdale 4 SW (92 km)
- Saco 1 NNW (93 km)
- Bredette (96 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.