Frost dates for Shonkin 7 S, MT
At Shonkin 7 S, 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 119 days. For a 90% chance that the last frost has passed, wait until Jun 10. Nearby ZIP codes are in USDA hardiness zones 4a to 4b.
- May 24Last spring frost (median)50% chance of 32°F after this date
- Jun 10Safer planting date10% chance of 32°F after this date
- Sep 21First fall frost (median)50% chance of 32°F by this date
- 119 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 6 | May 24 | Jun 10 |
| 28°F | Apr 22 | May 7 | May 27 |
| 24°F | Apr 6 | Apr 25 | May 10 |
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 31 | Sep 21 | Oct 5 |
| 28°F | Sep 16 | Oct 1 | Oct 19 |
| 24°F | Sep 26 | Oct 12 | Nov 1 |
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 | 60 days | 90 days | 114 days |
| 32°F | 94 days | 119 days | 144 days |
| 28°F | 122 days | 147 days | 170 days |
| 24°F | 145 days | 171 days | 197 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 59450 | 4b | -25 to -20°F | 13 km |
| 59447 | 4b | -25 to -20°F | 29 km |
| 59412 | 4b | -25 to -20°F | 33 km |
| 59446 | 4b | -25 to -20°F | 34 km |
| 59469 | 4b | -25 to -20°F | 39 km |
| 59424 | 4b | -25 to -20°F | 40 km |
| 59442 | 4a | -30 to -25°F | 45 km |
| 59440 | 4b | -25 to -20°F | 48 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 USC00247540, at 47.5314, -110.5764, elevation 1311 m (4,300 ft).
- Data quality: Representative (10+ years), 19 years of freeze data.
- Average days per year at or below 32°F: 147.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Highwood 7 NE (14 km)
- Geraldine (24 km)
- Raynesford 2 NNW (29 km)
- Fort Benton (34 km)
- Loma (45 km)
- Stanford (50 km)
- Great Falls 16st (53 km)
- Denton (54 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.