Frost dates for Joliet, MT
At Joliet, the median last spring frost (32°F) is May 29 and the median first fall frost is Sep 15, for a typical growing season of 107 days. For a 90% chance that the last frost has passed, wait until Jun 17. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 29Last spring frost (median)50% chance of 32°F after this date
- Jun 17Safer planting date10% chance of 32°F after this date
- Sep 15First fall frost (median)50% chance of 32°F by this date
- 107 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 30 | Jun 13 | Jun 30 |
| 32°F | May 14 | May 29 | Jun 17 |
| 28°F | May 1 | May 13 | May 31 |
| 24°F | Apr 17 | Apr 30 | May 14 |
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 22 | Sep 4 | Sep 17 |
| 32°F | Sep 1 | Sep 15 | Oct 1 |
| 28°F | Sep 11 | Sep 26 | Oct 9 |
| 24°F | Sep 22 | Oct 5 | Oct 21 |
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 | 56 days | 81 days | 101 days |
| 32°F | 86 days | 107 days | 127 days |
| 28°F | 113 days | 134 days | 153 days |
| 24°F | 136 days | 155 days | 176 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 |
|---|---|---|---|
| 59041 | 5a | -20 to -15°F | 5 km |
| 59013 | 5a | -20 to -15°F | 6 km |
| 59026 | 5a | -20 to -15°F | 18 km |
| 59070 | 5a | -20 to -15°F | 18 km |
| 59063 | 5a | -20 to -15°F | 20 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 USC00244506, at 45.4733, -109.0106, elevation 1170 m (3,838 ft).
- Data quality: Representative (10+ years), 24 years of freeze data.
- Average days per year at or below 32°F: 185.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Bridger 2 N (18 km)
- Columbus (28 km)
- Red Lodge (38 km)
- Billings WFO (46 km)
- Billings Logan Intl Airport (52 km)
- Billings Water Plant (53 km)
- Rapelje (59 km)
- Mystic Lake (62 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.