Frost dates for Virginia City, MT
At Virginia City, the median last spring frost (32°F) is Jun 4 and the median first fall frost is Sep 18, for a typical growing season of 106 days. For a 90% chance that the last frost has passed, wait until Jun 23. Nearby ZIP codes are in USDA hardiness zone 5a.
- Jun 4Last spring frost (median)50% chance of 32°F after this date
- Jun 23Safer planting date10% chance of 32°F after this date
- Sep 18First fall frost (median)50% chance of 32°F by this date
- 106 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 | Jun 5 | Jun 20 | Jul 6 |
| 32°F | May 17 | Jun 4 | Jun 23 |
| 28°F | May 1 | May 14 | Jun 3 |
| 24°F | Apr 17 | May 1 | May 16 |
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 23 | Sep 6 | Sep 20 |
| 32°F | Sep 3 | Sep 18 | Oct 2 |
| 28°F | Sep 13 | Oct 1 | Oct 14 |
| 24°F | Sep 25 | Oct 11 | Oct 27 |
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 | 54 days | 77 days | 98 days |
| 32°F | 83 days | 106 days | 128 days |
| 28°F | 112 days | 137 days | 158 days |
| 24°F | 141 days | 160 days | 182 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 |
|---|---|---|---|
| 59755 | 5a | -20 to -15°F | 2 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 USC00248597, at 45.2925, -111.9478, elevation 1760 m (5,773 ft).
- Data quality: Representative (10+ years), 26 years of freeze data.
- Average days per year at or below 32°F: 198.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Laurin 2ne (14 km)
- Ennis (19 km)
- Alder 19s (24 km)
- Alder 17 S (26 km)
- Norris Madison Power House (33 km)
- Twin Bridges (41 km)
- Dillon Airport (48 km)
- Big Sky 2wnw (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.