| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°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: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 80303 - Boulder, CO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 18 | 21 | 26 | 33 | 41 | 49 | 55 | 53 | 45 | 35 | 25 | 19 | 35 |
| Avg Max Temp (°F) | 44 | 48 | 54 | 62 | 71 | 81 | 87 | 84 | 77 | 66 | 52 | 45 | 64 |
| Avg Precip (In.) | .64 | .68 | 1.69 | 2.7 | 2.94 | 1.99 | 1.81 | 1.62 | 1.61 | 1.22 | 1.34 | .73 | 18.95 |