| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| Average First Frost Date: | Oct. 21 - Oct. 31 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year |
| Ecoregion: | 59a - Connecticut Valley |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 06422 - Durham, CT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 19 | 21 | 29 | 38 | 48 | 57 | 62 | 61 | 53 | 42 | 34 | 25 | 41 |
| Avg Max Temp (°F) | 36 | 38 | 47 | 59 | 70 | 79 | 84 | 81 | 72 | 61 | 51 | 40 | 60 |
| Avg Precip (In.) | 4.78 | 3.49 | 4.7 | 4.64 | 4.5 | 4.33 | 4.15 | 4.45 | 4.52 | 4.82 | 4.76 | 4.38 | 53.51 |