Frost dates for Rapelje, MT
At Rapelje, the median last spring frost (32°F) is May 24 and the median first fall frost is Sep 21, for a typical growing season of 116 days. For a 90% chance that the last frost has passed, wait until Jun 11. Nearby ZIP codes are in USDA hardiness zone 4b.
- May 24Last spring frost (median)50% chance of 32°F after this date
- Jun 11Safer planting date10% chance of 32°F after this date
- Sep 21First fall frost (median)50% chance of 32°F by this date
- 116 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 26 | Jun 8 | Jun 26 |
| 32°F | May 11 | May 24 | Jun 11 |
| 28°F | Apr 28 | May 11 | May 25 |
| 24°F | Apr 13 | Apr 30 | May 13 |
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 8 | Sep 23 |
| 32°F | Sep 4 | Sep 21 | Oct 4 |
| 28°F | Sep 18 | Oct 2 | Oct 16 |
| 24°F | Sep 29 | Oct 13 | Oct 26 |
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 | 65 days | 88 days | 111 days |
| 32°F | 93 days | 116 days | 138 days |
| 28°F | 121 days | 143 days | 162 days |
| 24°F | 146 days | 166 days | 184 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 |
|---|---|---|---|
| 59067 | 4b | -25 to -20°F | 2 km |
| 59057 | 4b | -25 to -20°F | 27 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 USC00246862, at 45.9717, -109.2536, elevation 1240 m (4,068 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 175.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Gibson 2 NE (20 km)
- Ryegate (36 km)
- Columbus (36 km)
- Roundup 15 SW (56 km)
- Big Timber (56 km)
- Billings Logan Intl Airport (58 km)
- Billings WFO (58 km)
- Joliet (59 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.