Frost dates for Rock Springs Airport, WY
At Rock Springs Airport, the median last spring frost (32°F) is May 22 and the median first fall frost is Sep 28, for a typical growing season of 126 days. For a 90% chance that the last frost has passed, wait until Jun 9. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- May 22Last spring frost (median)50% chance of 32°F after this date
- Jun 9Safer planting date10% chance of 32°F after this date
- Sep 28First fall frost (median)50% chance of 32°F by this date
- 126 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 21 | Jun 5 | Jun 21 |
| 32°F | May 5 | May 22 | Jun 9 |
| 28°F | Apr 23 | May 7 | May 25 |
| 24°F | Apr 10 | Apr 26 | May 10 |
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 | Sep 7 | Sep 19 | Sep 30 |
| 32°F | Sep 14 | Sep 28 | Oct 9 |
| 28°F | Sep 22 | Oct 5 | Oct 23 |
| 24°F | Sep 29 | Oct 17 | Nov 1 |
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 | 86 days | 104 days | 123 days |
| 32°F | 106 days | 126 days | 148 days |
| 28°F | 128 days | 149 days | 173 days |
| 24°F | 150 days | 171 days | 193 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 |
|---|---|---|---|
| 82945 | 5a | -20 to -15°F | 17 km |
| 82901 | 5b | -15 to -10°F | 25 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 USW00024027, at 41.5944, -109.0528, elevation 2055 m (6,741 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 189.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Rock Springs Fire Dept (16 km)
- Green River (36 km)
- Bitter Creek 4 NE (45 km)
- Buckboard Marina (60 km)
- Farson 2nne (68 km)
- Church Buttes Gas Plant (89 km)
- Wamsutter (90 km)
- Fontenelle Dam (94 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.