Frost dates for Whalen Dam Usbr, WY
At Whalen Dam Usbr, the median last spring frost (32°F) is May 7 and the median first fall frost is Oct 3, for a typical growing season of 146 days. For a 90% chance that the last frost has passed, wait until May 24. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 7Last spring frost (median)50% chance of 32°F after this date
- May 24Safer planting date10% chance of 32°F after this date
- Oct 3First fall frost (median)50% chance of 32°F by this date
- 146 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 7 | May 19 | Jun 6 |
| 32°F | Apr 25 | May 7 | May 24 |
| 28°F | Apr 14 | Apr 27 | May 10 |
| 24°F | Apr 3 | Apr 17 | May 2 |
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 9 | Sep 24 | Oct 6 |
| 32°F | Sep 21 | Oct 3 | Oct 14 |
| 28°F | Sep 29 | Oct 13 | Oct 25 |
| 24°F | Oct 8 | Oct 22 | 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 | 106 days | 125 days | 143 days |
| 32°F | 128 days | 146 days | 163 days |
| 28°F | 145 days | 164 days | 183 days |
| 24°F | 163 days | 185 days | 205 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 |
|---|---|---|---|
| 82212 | 5a | -20 to -15°F | 8 km |
| 82214 | 5a | -20 to -15°F | 10 km |
| 82223 | 5a | -20 to -15°F | 24 km |
| 82215 | 5a | -20 to -15°F | 25 km |
| 82219 | 5a | -20 to -15°F | 28 km |
| 82243 | 5a | -20 to -15°F | 34 km |
| 82213 | 5a | -20 to -15°F | 41 km |
| 82240 | 5a | -20 to -15°F | 42 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 USC00489604, at 42.2494, -104.6281, elevation 1309 m (4,294 ft).
- Data quality: Estimated from nearby stations (2+ years), 10 years of freeze data.
- Average days per year at or below 32°F: 174.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Old Fort Laramie (8 km)
- Guernsey Dam #2 (12 km)
- Guernsey 2nw (12 km)
- Lingle 2wsw (24 km)
- Wheatland 4 N (31 km)
- Glendo Rsvr Usbr (37 km)
- Torrington Exp. Farm (38 km)
- Glendo 6ne (39 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.