Frost dates for Rudyard 19s, MT
At Rudyard 19s, the median last spring frost (32°F) is May 23 and the median first fall frost is Sep 19, for a typical growing season of 119 days. For a 90% chance that the last frost has passed, wait until Jun 3. Nearby ZIP codes are in USDA hardiness zones 3b to 4a.
- May 23Last spring frost (median)50% chance of 32°F after this date
- Jun 3Safer planting date10% chance of 32°F after this date
- Sep 19First 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 |
|---|---|---|---|
| 36°F | May 24 | Jun 5 | Jun 24 |
| 32°F | May 12 | May 23 | Jun 3 |
| 28°F | May 2 | May 12 | May 22 |
| 24°F | Apr 17 | May 2 | 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 25 | Sep 8 | Sep 21 |
| 32°F | Sep 5 | Sep 19 | Oct 1 |
| 28°F | Sep 14 | Sep 27 | Oct 10 |
| 24°F | Sep 22 | Oct 5 | 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 | 70 days | 92 days | 111 days |
| 32°F | 102 days | 119 days | 134 days |
| 28°F | 122 days | 138 days | 155 days |
| 24°F | 140 days | 156 days | 176 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 |
|---|---|---|---|
| 59460 | 4a | -30 to -25°F | 24 km |
| 59540 | 3b | -35 to -30°F | 37 km |
| 59530 | 4a | -30 to -25°F | 37 km |
| 59442 | 4a | -30 to -25°F | 39 km |
| 59528 | 4a | -30 to -25°F | 40 km |
| 59522 | 4a | -30 to -25°F | 42 km |
| 59525 | 3b | -35 to -30°F | 48 km |
| 59521 | 4a | -30 to -25°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 USC00247247, at 48.2775, -110.6022, elevation 877 m (2,878 ft).
- Data quality: Representative (10+ years), 19 years of freeze data.
- Average days per year at or below 32°F: 196.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Joplin (34 km)
- Tiber Dam (36 km)
- Chester (37 km)
- Loma (39 km)
- Gildford (39 km)
- Big Sandy (43 km)
- Fort Benton (50 km)
- Brady 27 ENE (the Knees) (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.