| 2023 Hardiness Zone: | Zone 6b: -5°F to 0°F Zone 7a: 0°F to 5°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. 21 - Oct. 31 |
| Average Last Frost Date: | Apr. 21 - Apr. 30 |
| Koppen-Geiger Climate Zone: | Dfa - Humid Continental Hot Summers |
| Ecoregion: | 59a - Connecticut Valley |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 06518 - Hamden, CT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 18 | 20 | 28 | 37 | 47 | 57 | 62 | 61 | 53 | 41 | 33 | 24 | 40 |
| Avg Max Temp (°F) | 35 | 37 | 46 | 58 | 68 | 78 | 83 | 80 | 73 | 62 | 50 | 40 | 59 |
| Avg Precip (In.) | 4.63 | 3.33 | 4.7 | 4.61 | 4.71 | 4.43 | 4.25 | 4.44 | 4.62 | 4.56 | 4.62 | 4.19 | 53.09 |