| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | BSk - Cold Semi-Arid Climate |
| Ecoregion: | 25d - Flat to Rolling Plains |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 80241 - Thornton, CO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 17 | 20 | 26 | 34 | 43 | 52 | 58 | 57 | 47 | 36 | 25 | 18 | 36 |
| Avg Max Temp (°F) | 44 | 48 | 54 | 61 | 71 | 82 | 87 | 86 | 77 | 66 | 51 | 44 | 64 |
| Avg Precip (In.) | .39 | .35 | .99 | 1.85 | 2.29 | 1.58 | 1.65 | 1.36 | .95 | .83 | .83 | .47 | 13.54 |