Frost dates for Northglenn, CO
At Northglenn, the median last spring frost (32°F) is May 2 and the median first fall frost is Oct 11, for a typical growing season of 160 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zone 6a.
- May 2Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 11First 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 | Apr 30 | May 12 | May 26 |
| 32°F | Apr 18 | May 2 | May 14 |
| 28°F | Apr 4 | Apr 20 | May 5 |
| 24°F | Mar 19 | Apr 6 | 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 18 | Oct 1 | Oct 14 |
| 32°F | Sep 26 | Oct 11 | Oct 24 |
| 28°F | Oct 7 | Oct 21 | Nov 4 |
| 24°F | Oct 15 | Oct 31 | Nov 14 |
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 | 122 days | 142 days | 159 days |
| 32°F | 142 days | 160 days | 180 days |
| 28°F | 160 days | 182 days | 204 days |
| 24°F | 181 days | 205 days | 230 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 |
|---|---|---|---|
| 80234 | 6a | -10 to -5°F | 2 km |
| 80031 | 6a | -10 to -5°F | 4 km |
| 80260 | 6a | -10 to -5°F | 4 km |
| 80233 | 6a | -10 to -5°F | 6 km |
| 80241 | 6a | -10 to -5°F | 6 km |
| 80020 | 6a | -10 to -5°F | 6 km |
| 80229 | 6a | -10 to -5°F | 7 km |
| 80030 | 6a | -10 to -5°F | 8 km |
| 80023 | 6a | -10 to -5°F | 9 km |
| 80021 | 6a | -10 to -5°F | 9 km |
| 80221 | 6a | -10 to -5°F | 9 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 USC00055984, at 39.8989, -105.0133, elevation 1648 m (5,407 ft).
- Data quality: Standard (24+ years of data), 26 years of freeze data.
- Average days per year at or below 32°F: 149.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Brighton 3 SE (16 km)
- Wheat Ridge 2 (16 km)
- Denver Water Dept (19 km)
- Lakewood (19 km)
- Denver-Stapleton (19 km)
- Ralston Rsvr (20 km)
- Boulder (24 km)
- Gross Rsvr (29 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.