| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Cfa - Humid Subtropical Climate |
| Ecoregion: | 25l - Front Range Fans |
| Heat Zone Days: | 8 - 14 days Over 86°F |
Annual Climate Data for ZIP Code 80305 - Boulder, CO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 16 | 20 | 25 | 32 | 39 | 48 | 53 | 52 | 44 | 34 | 24 | 18 | 34 |
| Avg Max Temp (°F) | 44 | 47 | 53 | 60 | 69 | 80 | 85 | 83 | 75 | 65 | 51 | 45 | 63 |
| Avg Precip (In.) | .58 | .55 | 1.44 | 2.41 | 2.84 | 1.92 | 1.69 | 1.66 | 1.51 | 1.02 | 1.11 | .66 | 17.39 |