Frost dates for Boulder, UT
At Boulder, the median last spring frost (32°F) is May 4 and the median first fall frost is Oct 14, for a typical growing season of 160 days. For a 90% chance that the last frost has passed, wait until May 25. Nearby ZIP codes are in USDA hardiness zone 7a.
- May 4Last spring frost (median)50% chance of 32°F after this date
- May 25Safer planting date10% chance of 32°F after this date
- Oct 14First fall frost (median)50% chance of 32°F by this date
- 160 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 1 | May 18 | Jun 6 |
| 32°F | Apr 20 | May 4 | May 25 |
| 28°F | Apr 5 | Apr 23 | May 12 |
| 24°F | Mar 14 | Apr 8 | Apr 26 |
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 22 | Oct 5 | Oct 18 |
| 32°F | Sep 30 | Oct 14 | Oct 29 |
| 28°F | Oct 7 | Oct 23 | Nov 9 |
| 24°F | Oct 18 | Nov 4 | Nov 20 |
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 | 113 days | 137 days | 160 days |
| 32°F | 135 days | 160 days | 182 days |
| 28°F | 160 days | 182 days | 206 days |
| 24°F | 181 days | 208 days | 237 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 |
|---|---|---|---|
| 84716 | 7a | 0 to 5°F | 5 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 USC00420849, at 37.9050, -111.4200, elevation 2027 m (6,650 ft).
- Data quality: Standard (24+ years of data), 25 years of freeze data.
- Average days per year at or below 32°F: 146.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Escalante (22 km)
- Capitol Reef National Park (45 km)
- Torrey 7 E (46 km)
- Loa (59 km)
- Angle (61 km)
- Kodachrome Basin Park (66 km)
- Bryce Canyon Airport (67 km)
- Bryce Canyon National Park Hqrs (72 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.