| 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 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: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 80301 - Boulder, CO | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 17 | 21 | 27 | 34 | 43 | 51 | 56 | 55 | 46 | 36 | 26 | 19 | 36 |
| Avg Max Temp (°F) | 45 | 49 | 54 | 63 | 72 | 83 | 88 | 86 | 78 | 67 | 52 | 45 | 65 |
| Avg Precip (In.) | .53 | .54 | 1.39 | 2.33 | 2.65 | 1.85 | 1.66 | 1.56 | 1.4 | 1.02 | 1.06 | .61 | 16.6 |