Frost dates for Plentywood, MT
At Plentywood, the median last spring frost (32°F) is May 25 and the median first fall frost is Sep 14, for a typical growing season of 111 days. For a 90% chance that the last frost has passed, wait until Jun 8. Nearby ZIP codes are in USDA hardiness zone 3b.
- May 25Last spring frost (median)50% chance of 32°F after this date
- Jun 8Safer planting date10% chance of 32°F after this date
- Sep 14First fall frost (median)50% chance of 32°F by this date
- 111 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 23 | Jun 6 | Jun 29 |
| 32°F | May 13 | May 25 | Jun 8 |
| 28°F | May 3 | May 15 | May 28 |
| 24°F | Apr 23 | May 6 | May 19 |
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 | Aug 21 | Sep 4 | Sep 15 |
| 32°F | Sep 2 | Sep 14 | Sep 25 |
| 28°F | Sep 9 | Sep 22 | Oct 3 |
| 24°F | Sep 16 | Sep 29 | Oct 13 |
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 | 61 days | 88 days | 108 days |
| 32°F | 93 days | 111 days | 128 days |
| 28°F | 111 days | 129 days | 146 days |
| 24°F | 128 days | 146 days | 166 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 |
|---|---|---|---|
| 59254 | 3b | -35 to -30°F | 6 km |
| 59211 | 3b | -35 to -30°F | 18 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 USC00246586, at 48.7747, -104.5672, elevation 624 m (2,048 ft).
- Data quality: Representative (10+ years), 24 years of freeze data.
- Average days per year at or below 32°F: 204.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Raymond Border Station (25 km)
- Redstone (28 km)
- Medicine Lake 3 SE (34 km)
- Westby (39 km)
- Wolf Point 34 NE (57 km)
- Bredette (61 km)
- Wolf Point 29 ENE (65 km)
- Scobey 4 NW (67 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.