Frost dates for Alton, UT
At Alton, the median last spring frost (32°F) is Jun 1 and the median first fall frost is Sep 30, for a typical growing season of 120 days. For a 90% chance that the last frost has passed, wait until Jun 15. Nearby ZIP codes are in USDA hardiness zone 6a.
- Jun 1Last spring frost (median)50% chance of 32°F after this date
- Jun 15Safer planting date10% chance of 32°F after this date
- Sep 30First fall frost (median)50% chance of 32°F by this date
- 120 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 30 | Jun 11 | Jun 24 |
| 32°F | May 16 | Jun 1 | Jun 15 |
| 28°F | Apr 29 | May 17 | Jun 4 |
| 24°F | Apr 13 | May 1 | May 20 |
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 20 | Oct 1 |
| 32°F | Sep 16 | Sep 30 | Oct 12 |
| 28°F | Sep 27 | Oct 11 | Oct 24 |
| 24°F | Oct 9 | Oct 23 | Nov 8 |
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 | 81 days | 99 days | 115 days |
| 32°F | 101 days | 120 days | 141 days |
| 28°F | 123 days | 147 days | 168 days |
| 24°F | 151 days | 174 days | 197 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 |
|---|---|---|---|
| 84710 | 6a | -10 to -5°F | 4 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 USC00420086, at 37.4403, -112.4819, elevation 2164 m (7,098 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 190.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Orderville (23 km)
- Hatch (24 km)
- Bryce Canyon National Park Hqrs (35 km)
- Cedar Breaks National Monument (37 km)
- Blowhard Mountain Radar (38 km)
- Bryce Canyon Airport (42 km)
- Panguitch (42 km)
- Brian Head (43 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.