Frost dates for Blowhard Mountain Radar, UT
At Blowhard Mountain Radar, the median last spring frost (32°F) is Jun 7 and the median first fall frost is Sep 29, for a typical growing season of 110 days. For a 90% chance that the last frost has passed, wait until Jun 22. Nearby ZIP codes are in USDA hardiness zones 6a to 6b.
- Jun 7Last spring frost (median)50% chance of 32°F after this date
- Jun 22Safer planting date10% chance of 32°F after this date
- Sep 29First fall frost (median)50% chance of 32°F by this date
- 110 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 | Jun 4 | Jun 16 | Jul 1 |
| 32°F | May 25 | Jun 7 | Jun 22 |
| 28°F | May 11 | May 30 | Jun 13 |
| 24°F | Apr 29 | May 13 | Jun 3 |
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 4 | Sep 19 | Oct 1 |
| 32°F | Sep 14 | Sep 29 | Oct 12 |
| 28°F | Sep 22 | Oct 6 | Oct 21 |
| 24°F | Oct 1 | Oct 16 | 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 | 71 days | 92 days | 111 days |
| 32°F | 90 days | 110 days | 131 days |
| 28°F | 108 days | 129 days | 150 days |
| 24°F | 128 days | 153 days | 176 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 |
|---|---|---|---|
| 84719 | 6a | -10 to -5°F | 10 km |
| 84762 | 6a | -10 to -5°F | 15 km |
| 84772 | 6b | -5 to 0°F | 23 km |
| 84742 | 6b | -5 to 0°F | 27 km |
| 84761 | 6a | -10 to -5°F | 29 km |
| 84729 | 6b | -5 to 0°F | 29 km |
| 84758 | 6b | -5 to 0°F | 31 km |
| 84721 | 6b | -5 to 0°F | 31 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 USC00420757, at 37.5928, -112.8639, elevation 3260 m (10,694 ft).
- Data quality: Representative (10+ years), 13 years of freeze data.
- Average days per year at or below 32°F: 204.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Cedar Breaks National Monument (3 km)
- Brian Head (11 km)
- Cedar City 5e (13 km)
- Cedar City (21 km)
- Cedar City Muni Airport (24 km)
- Alton (38 km)
- Hatch (38 km)
- New Harmony (40 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.