| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F | |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F 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: | May 1 - May 10 | |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year | |
| Ecoregion: | 59c - Southern New England Coastal Plains and Hills | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 06438 - Haddam, CT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 18 | 20 | 28 | 36 | 46 | 56 | 61 | 60 | 52 | 41 | 33 | 24 | 40 |
| Avg Max Temp (°F) | 37 | 39 | 47 | 59 | 69 | 78 | 83 | 81 | 73 | 63 | 51 | 41 | 60 |
| Avg Precip (In.) | 4.91 | 3.54 | 4.66 | 4.64 | 4.19 | 4.12 | 3.88 | 4.59 | 4.19 | 4.64 | 4.84 | 4.49 | 52.68 |