Frost dates for White Sulphur Springs #2, MT
At White Sulphur Springs #2, the median last spring frost (32°F) is Jun 4 and the median first fall frost is Sep 11, for a typical growing season of 97 days. For a 90% chance that the last frost has passed, wait until Jun 20. Nearby ZIP codes are in USDA hardiness zone 4b.
- Jun 4Last spring frost (median)50% chance of 32°F after this date
- Jun 20Safer planting date10% chance of 32°F after this date
- Sep 11First fall frost (median)50% chance of 32°F by this date
- 97 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 21 | Jun 4 | Jun 20 |
| 28°F | May 5 | May 18 | Jun 1 |
| 24°F | Apr 22 | May 5 | May 18 |
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 27 | Sep 11 | Sep 27 |
| 28°F | Sep 10 | Sep 25 | Oct 7 |
| 24°F | Sep 21 | Oct 4 | Oct 19 |
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 | 42 days | 65 days | 89 days |
| 32°F | 74 days | 97 days | 119 days |
| 28°F | 108 days | 128 days | 149 days |
| 24°F | 133 days | 151 days | 170 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 |
|---|---|---|---|
| 59645 | 4b | -25 to -20°F | 20 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 USC00248930, at 46.5436, -110.9000, elevation 1536 m (5,040 ft).
- Data quality: Representative (10+ years), 24 years of freeze data.
- Average days per year at or below 32°F: 199.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Lennep 5 SW (31 km)
- Millegan 14 SE (42 km)
- Martinsdale 3 NNW (43 km)
- Townsend 3se (50 km)
- Neihart 8 NNW (56 km)
- Lewistown 42 WSW (60 km)
- Wilsall 1s (65 km)
- Wilsall 8 ENE (65 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.