| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°F |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| Average First Frost Date: | Oct. 11 - Oct. 20 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year |
| Ecoregion: | 59c - Southern New England Coastal Plains and Hills |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 06417 - Deep River, CT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 18 | 20 | 27 | 35 | 45 | 55 | 61 | 59 | 52 | 41 | 33 | 24 | 39 |
| Avg Max Temp (°F) | 38 | 40 | 48 | 58 | 68 | 77 | 82 | 81 | 73 | 64 | 52 | 42 | 60 |
| Avg Precip (In.) | 4.64 | 3.5 | 4.59 | 4.51 | 4.15 | 3.9 | 3.79 | 4.41 | 4.13 | 4.42 | 4.69 | 4.36 | 51.09 |