| 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: | Dfb - Humid Continental Mild Summer, Wet All Year |
| Ecoregion: | 25l - Front Range Fans |
| Heat Zone Days: | 8 - 14 days Over 86°F |
Annual Climate Data for ZIP Code 80304 - Boulder, CO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 17 | 20 | 26 | 32 | 40 | 48 | 53 | 52 | 44 | 34 | 25 | 19 | 34 |
| Avg Max Temp (°F) | 44 | 47 | 52 | 60 | 69 | 80 | 85 | 83 | 76 | 65 | 51 | 44 | 63 |
| Avg Precip (In.) | .67 | .7 | 1.75 | 2.71 | 3.06 | 2.07 | 1.89 | 1.66 | 1.79 | 1.21 | 1.3 | .79 | 19.59 |