Frost dates for Strontia Springs Dam, CO
At Strontia Springs Dam, the median last spring frost (32°F) is May 16 and the median first fall frost is Sep 29, for a typical growing season of 132 days. For a 90% chance that the last frost has passed, wait until Jun 6. Nearby ZIP codes are in USDA hardiness zone 5b.
- May 16Last spring frost (median)50% chance of 32°F after this date
- Jun 6Safer planting date10% chance of 32°F after this date
- Sep 29First fall frost (median)50% chance of 32°F by this date
- 132 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 17 | Jun 1 | Jun 16 |
| 32°F | May 3 | May 16 | Jun 6 |
| 28°F | Apr 21 | May 3 | May 19 |
| 24°F | Apr 7 | Apr 23 | May 7 |
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 8 | Sep 21 | Oct 1 |
| 32°F | Sep 16 | Sep 29 | Oct 11 |
| 28°F | Sep 25 | Oct 8 | Oct 22 |
| 24°F | Oct 4 | Oct 17 | Nov 2 |
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 | 89 days | 108 days | 128 days |
| 32°F | 110 days | 132 days | 152 days |
| 28°F | 134 days | 156 days | 174 days |
| 24°F | 159 days | 177 days | 200 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 |
|---|---|---|---|
| 80425 | 5b | -15 to -10°F | 12 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 USC00058022, at 39.4344, -105.1208, elevation 1780 m (5,840 ft).
- Data quality: Representative (10+ years), 19 years of freeze data.
- Average days per year at or below 32°F: 207.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Roxborough State Park (4 km)
- Kassler (7 km)
- Castle Rock (19 km)
- Marston Fltr Plant (21 km)
- Cheesman (27 km)
- Denver Centennial Airport (28 km)
- Evergreen (28 km)
- Bailey (31 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.