Frost dates for Millegan 14 SE, MT
At Millegan 14 SE, the median last spring frost (32°F) is Jun 11 and the median first fall frost is Sep 6, for a typical growing season of 86 days. For a 90% chance that the last frost has passed, wait until Jul 3. Nearby ZIP codes are in USDA hardiness zone 4b.
- Jun 11Last spring frost (median)50% chance of 32°F after this date
- Jul 3Safer planting date10% chance of 32°F after this date
- Sep 6First fall frost (median)50% chance of 32°F by this date
- 86 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 27 | Jun 11 | Jul 3 |
| 28°F | May 8 | May 20 | Jun 7 |
| 24°F | Apr 23 | May 6 | 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 20 | Sep 6 | Sep 21 |
| 28°F | Sep 6 | Sep 22 | Oct 5 |
| 24°F | Sep 18 | Oct 2 | Oct 16 |
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 | 30 days | 49 days | 74 days |
| 32°F | 58 days | 86 days | 108 days |
| 28°F | 97 days | 121 days | 141 days |
| 24°F | 127 days | 147 days | 165 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 |
|---|---|---|---|
| 59645 | 4b | -25 to -20°F | 22 km |
| 59463 | 4b | -25 to -20°F | 30 km |
| 59465 | 4b | -25 to -20°F | 35 km |
| 59480 | 4b | -25 to -20°F | 38 km |
| 59421 | 4b | -25 to -20°F | 46 km |
| 59405 | 4b | -25 to -20°F | 47 km |
| 59469 | 4b | -25 to -20°F | 51 km |
| 59472 | 4b | -25 to -20°F | 52 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 USC00245712, at 46.8747, -111.1642, elevation 1515 m (4,970 ft).
- Data quality: Standard (24+ years of data), 25 years of freeze data.
- Average days per year at or below 32°F: 215.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Cascade 20 SSE (34 km)
- Neihart 8 NNW (35 km)
- Adel (42 km)
- White Sulphur Springs #2 (42 km)
- Cascade 5 S (56 km)
- Raynesford 2 NNW (57 km)
- Holter Dam (66 km)
- Lewistown 42 WSW (66 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.