Frost dates for Judith Gap 13 E, MT
At Judith Gap 13 E, the median last spring frost (32°F) is Jun 3 and the median first fall frost is Sep 15, for a typical growing season of 100 days. For a 90% chance that the last frost has passed, wait until Jun 25. Nearby ZIP codes are in USDA hardiness zone 4b.
- Jun 3Last spring frost (median)50% chance of 32°F after this date
- Jun 25Safer planting date10% chance of 32°F after this date
- Sep 15First fall frost (median)50% chance of 32°F by this date
- 100 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 19 | Jun 3 | Jun 25 |
| 28°F | May 5 | May 19 | Jun 6 |
| 24°F | Apr 21 | May 6 | May 23 |
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 29 | Sep 15 | Sep 29 |
| 28°F | Sep 14 | Sep 27 | Oct 9 |
| 24°F | Sep 24 | 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 | 43 days | 71 days | 94 days |
| 32°F | 69 days | 100 days | 123 days |
| 28°F | 104 days | 129 days | 148 days |
| 24°F | 131 days | 152 days | 172 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 |
|---|---|---|---|
| 59453 | 4b | -25 to -20°F | 16 km |
| 59078 | 4b | -25 to -20°F | 21 km |
| 59464 | 4b | -25 to -20°F | 28 km |
| 59074 | 4b | -25 to -20°F | 30 km |
| 59036 | 4b | -25 to -20°F | 36 km |
| 59418 | 4b | -25 to -20°F | 36 km |
| 59441 | 4b | -25 to -20°F | 39 km |
| 59046 | 4b | -25 to -20°F | 49 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 USC00244545, at 46.6103, -109.4736, elevation 1460 m (4,791 ft).
- Data quality: Representative (10+ years), 19 years of freeze data.
- Average days per year at or below 32°F: 203.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ryegate 18 NNW (13 km)
- Judith Gap (22 km)
- Lewistown 11 SSE (33 km)
- Harlowton (34 km)
- Harlowton 11nw (36 km)
- Ryegate (38 km)
- Lewistown 11ese (48 km)
- Lewistown Muni Airport (49 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.