Frost dates for Hungry Horse Dam, MT
At Hungry Horse Dam, the median last spring frost (32°F) is May 9 and the median first fall frost is Oct 1, for a typical growing season of 141 days. For a 90% chance that the last frost has passed, wait until May 30. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- May 9Last spring frost (median)50% chance of 32°F after this date
- May 30Safer planting date10% chance of 32°F after this date
- Oct 1First fall frost (median)50% chance of 32°F by this date
- 141 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 10 | May 28 | Jun 19 |
| 32°F | Apr 25 | May 9 | May 30 |
| 28°F | Apr 8 | Apr 27 | May 14 |
| 24°F | Mar 23 | Apr 14 | May 5 |
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 31 | Sep 19 | Oct 2 |
| 32°F | Sep 13 | Oct 1 | Oct 17 |
| 28°F | Sep 30 | Oct 14 | Oct 31 |
| 24°F | Oct 7 | Oct 28 | Nov 15 |
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 | 80 days | 110 days | 135 days |
| 32°F | 111 days | 141 days | 165 days |
| 28°F | 141 days | 170 days | 195 days |
| 24°F | 167 days | 196 days | 224 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 |
|---|---|---|---|
| 59926 | 5b | -15 to -10°F | 2 km |
| 59919 | 5b | -15 to -10°F | 5 km |
| 59916 | 5a | -20 to -15°F | 27 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 USC00244328, at 48.3425, -114.0217, elevation 963 m (3,160 ft).
- Data quality: Representative (10+ years), 26 years of freeze data.
- Average days per year at or below 32°F: 169.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- W Glacier (18 km)
- Kalispell Glacier Airport (18 km)
- Creston (19 km)
- Whitefish (26 km)
- Olney (47 km)
- Swan Lake (49 km)
- Polebridge (51 km)
- Bigfork 13 S (52 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.