Frost dates for Eureka Ranger Station, MT
At Eureka Ranger Station, the median last spring frost (32°F) is May 11 and the median first fall frost is Sep 27, for a typical growing season of 138 days. For a 90% chance that the last frost has passed, wait until May 25. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- May 11Last spring frost (median)50% chance of 32°F after this date
- May 25Safer planting date10% chance of 32°F after this date
- Sep 27First fall frost (median)50% chance of 32°F by this date
- 138 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 12 | May 26 | Jun 8 |
| 32°F | Apr 28 | May 11 | May 25 |
| 28°F | Apr 10 | Apr 28 | May 12 |
| 24°F | Mar 23 | Apr 10 | Apr 30 |
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 28 | Sep 13 | Sep 30 |
| 32°F | Sep 10 | Sep 27 | Oct 9 |
| 28°F | Sep 26 | Oct 7 | Oct 26 |
| 24°F | Oct 4 | Oct 20 | Nov 7 |
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 | 87 days | 109 days | 129 days |
| 32°F | 116 days | 138 days | 156 days |
| 28°F | 143 days | 164 days | 188 days |
| 24°F | 167 days | 193 days | 218 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 |
|---|---|---|---|
| 59930 | 5b | -15 to -10°F | 6 km |
| 59917 | 5a | -20 to -15°F | 14 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 USC00242827, at 48.8978, -115.0644, elevation 772 m (2,532 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 153.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Fortine 1 N (18 km)
- Yaak 9nne (42 km)
- Olney (53 km)
- Libby Dam (base) (57 km)
- Polebridge (59 km)
- Libby 1 NE Ranger Station (65 km)
- Libby (68 km)
- Whitefish (75 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.