Frost dates for Sundance 8 NNW, WY
At Sundance 8 NNW, the median last spring frost (32°F) is May 23 and the median first fall frost is Sep 24, for a typical growing season of 121 days. For a 90% chance that the last frost has passed, wait until Jun 3. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 23Last spring frost (median)50% chance of 32°F after this date
- Jun 3Safer planting date10% chance of 32°F after this date
- Sep 24First fall frost (median)50% chance of 32°F by this date
- 121 daysGrowing season (median)between 32°F freezes
USDA hardiness zone 5a (-20 to -15°F) · see all zone 5a frost dates
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 23 | Jun 5 | Jun 20 |
| 32°F | May 10 | May 23 | Jun 3 |
| 28°F | Apr 30 | May 12 | May 25 |
| 24°F | Apr 18 | 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 28 | Sep 11 | Sep 27 |
| 32°F | Sep 7 | Sep 24 | Oct 8 |
| 28°F | Sep 18 | Oct 4 | Oct 18 |
| 24°F | Sep 27 | Oct 13 | Oct 29 |
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 | 77 days | 97 days | 117 days |
| 32°F | 103 days | 121 days | 142 days |
| 28°F | 123 days | 143 days | 163 days |
| 24°F | 141 days | 163 days | 186 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 |
|---|---|---|---|
| 82710 | 5a | -20 to -15°F | 22 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 USW00094088, at 44.5169, -104.4364, elevation 1765 m (5,792 ft).
- Data quality: Representative (10+ years), 13 years of freeze data.
- Average days per year at or below 32°F: 182.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Sundance (13 km)
- Hulett (23 km)
- Devils Twr #2 (23 km)
- Colony (45 km)
- Upton (49 km)
- Moorcroft 3S (51 km)
- Weston 1 E (70 km)
- Dillinger (71 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.