Frost dates for Kassler, CO
At Kassler, the median last spring frost (32°F) is May 8 and the median first fall frost is Oct 3, for a typical growing season of 147 days. For a 90% chance that the last frost has passed, wait until May 22. Nearby ZIP codes are in USDA hardiness zone 5b.
- May 8Last spring frost (median)50% chance of 32°F after this date
- May 22Safer planting date10% chance of 32°F after this date
- Oct 3First fall frost (median)50% chance of 32°F by this date
- 147 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 5 | May 19 | Jun 2 |
| 32°F | Apr 27 | May 8 | May 22 |
| 28°F | Apr 15 | Apr 29 | May 13 |
| 24°F | Mar 31 | Apr 17 | May 1 |
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 13 | Sep 27 | Oct 8 |
| 32°F | Sep 21 | Oct 3 | Oct 17 |
| 28°F | Sep 28 | Oct 13 | Oct 28 |
| 24°F | Oct 7 | Oct 23 | Nov 7 |
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 | 110 days | 128 days | 146 days |
| 32°F | 126 days | 147 days | 165 days |
| 28°F | 146 days | 167 days | 187 days |
| 24°F | 168 days | 190 days | 212 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 |
|---|---|---|---|
| 80125 | 5b | -15 to -10°F | 3 km |
| 80127 | 5b | -15 to -10°F | 7 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 USC00054452, at 39.4900, -105.0953, elevation 1703 m (5,587 ft).
- Data quality: Representative (10+ years), 23 years of freeze data.
- Average days per year at or below 32°F: 156.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Strontia Springs Dam (7 km)
- Roxborough State Park (7 km)
- Marston Fltr Plant (15 km)
- Castle Rock (19 km)
- Denver Centennial Airport (23 km)
- Evergreen (25 km)
- Cherry Creek Dam (27 km)
- Denver Water Dept (28 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.