Frost dates for Diversion Dam, WY
At Diversion Dam, the median last spring frost (32°F) is May 21 and the median first fall frost is Sep 20, for a typical growing season of 119 days. For a 90% chance that the last frost has passed, wait until Jun 6. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 21Last spring frost (median)50% chance of 32°F after this date
- Jun 6Safer planting date10% chance of 32°F after this date
- Sep 20First fall frost (median)50% chance of 32°F by this date
- 119 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 24 | Jun 9 | Jun 27 |
| 32°F | May 7 | May 21 | Jun 6 |
| 28°F | Apr 26 | May 8 | May 22 |
| 24°F | Apr 16 | Apr 30 | May 11 |
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 27 | Sep 10 | Sep 24 |
| 32°F | Sep 5 | Sep 20 | Oct 4 |
| 28°F | Sep 15 | Oct 1 | Oct 16 |
| 24°F | Sep 25 | 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 | 70 days | 93 days | 112 days |
| 32°F | 97 days | 119 days | 139 days |
| 28°F | 124 days | 143 days | 164 days |
| 24°F | 143 days | 163 days | 184 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 |
|---|---|---|---|
| 82516 | 5a | -20 to -15°F | 7 km |
| 82523 | 5a | -20 to -15°F | 20 km |
| 82514 | 5a | -20 to -15°F | 21 km |
| 82512 | 5a | -20 to -15°F | 35 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 USC00482595, at 43.2336, -108.9133, elevation 1700 m (5,578 ft).
- Data quality: Representative (10+ years), 26 years of freeze data.
- Average days per year at or below 32°F: 200.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Pavillion (18 km)
- Burris (33 km)
- Riverton (40 km)
- Lander Hunt Field Airport (49 km)
- Riverton (49 km)
- Thermopolis 21wnw (57 km)
- Boysen Dam (64 km)
- Shoshoni (65 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.