| 2023 Hardiness Zone: | Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F | |
| 2012 Hardiness Zone: | Zone 7a: 0°F to 5°F | |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F | |
| Average First Frost Date: | Oct. 21 - Oct. 31 | |
| Average Last Frost Date: | Apr. 11 - Apr. 20 | |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers | |
| 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 06870 - Old Greenwich, CT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 21 | 23 | 30 | 39 | 50 | 59 | 64 | 63 | 55 | 44 | 36 | 27 | 43 |
| Avg Max Temp (°F) | 37 | 40 | 49 | 60 | 70 | 79 | 84 | 83 | 75 | 64 | 53 | 42 | 61 |
| Avg Precip (In.) | 4.21 | 3.09 | 4.38 | 4.32 | 4.54 | 3.98 | 4.07 | 4.17 | 4.56 | 4 | 4.27 | 3.98 | 49.58 |