Frost dates for Sybille Rsch Unit, WY
At Sybille Rsch Unit, the median last spring frost (32°F) is May 22 and the median first fall frost is Sep 24, for a typical growing season of 125 days. For a 90% chance that the last frost has passed, wait until Jun 5. Nearby ZIP codes are in USDA hardiness zones 4a to 5b.
- May 22Last spring frost (median)50% chance of 32°F after this date
- Jun 5Safer planting date10% chance of 32°F after this date
- Sep 24First fall frost (median)50% chance of 32°F by this date
- 125 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 22 | Jun 4 | Jun 18 |
| 32°F | May 8 | May 22 | Jun 5 |
| 28°F | Apr 25 | May 7 | May 21 |
| 24°F | Apr 12 | Apr 28 | 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 | Sep 1 | Sep 14 | Sep 28 |
| 32°F | Sep 9 | Sep 24 | Oct 7 |
| 28°F | Sep 19 | Oct 4 | Oct 17 |
| 24°F | Oct 1 | Oct 14 | 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 | 79 days | 99 days | 119 days |
| 32°F | 103 days | 125 days | 144 days |
| 28°F | 129 days | 149 days | 168 days |
| 24°F | 148 days | 169 days | 192 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 |
|---|---|---|---|
| 82051 | 4a | -30 to -25°F | 29 km |
| 82061 | 5b | -15 to -10°F | 36 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 USC00488808, at 41.7644, -105.3750, elevation 1855 m (6,086 ft).
- Data quality: Representative (10+ years), 21 years of freeze data.
- Average days per year at or below 32°F: 184.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Chugwater (46 km)
- Double Four Rch (46 km)
- Laramie 2 NW (51 km)
- Wheatland 4 N (52 km)
- Laramie 4se (55 km)
- Laramie Regional Airport (56 km)
- Medicine Bow (70 km)
- Hecla 1e (70 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.