Frost dates for Powell Field Station, WY
At Powell Field Station, the median last spring frost (32°F) is May 19 and the median first fall frost is Sep 20, for a typical growing season of 123 days. For a 90% chance that the last frost has passed, wait until Jun 4. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 19Last spring frost (median)50% chance of 32°F after this date
- Jun 4Safer planting date10% chance of 32°F after this date
- Sep 20First fall frost (median)50% chance of 32°F by this date
- 123 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 |
|---|---|---|---|
| 32°F | May 5 | May 19 | Jun 4 |
| 28°F | Apr 25 | May 5 | May 20 |
| 24°F | Apr 11 | Apr 25 | May 7 |
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 |
|---|---|---|---|
| 32°F | Sep 7 | Sep 20 | Oct 1 |
| 28°F | Sep 16 | Sep 29 | Oct 14 |
| 24°F | Sep 26 | Oct 10 | Oct 25 |
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 | 63 days | 94 days | 117 days |
| 32°F | 102 days | 123 days | 141 days |
| 28°F | 127 days | 146 days | 164 days |
| 24°F | 146 days | 167 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% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 82440 | 5a | -20 to -15°F | 11 km |
| 82412 | 5a | -20 to -15°F | 16 km |
| 82421 | 5a | -20 to -15°F | 17 km |
| 82435 | 5a | -20 to -15°F | 24 km |
| 82423 | 5a | -20 to -15°F | 27 km |
| 82420 | 5a | -20 to -15°F | 28 km |
| 59008 | 5a | -20 to -15°F | 42 km |
| 82411 | 5a | -20 to -15°F | 43 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 USC00487388, at 44.7764, -108.7592, elevation 1333 m (4,372 ft).
- Data quality: Standard (24+ years of data), 26 years of freeze data.
- Average days per year at or below 32°F: 191.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Heart Mountain (17 km)
- Deaver (18 km)
- Lovell (29 km)
- Clark 3ne (35 km)
- Cody (41 km)
- Cody 12se (42 km)
- Emblem (43 km)
- Buffalo Bill Dam (44 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.