| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 5a: -20F to -15F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year |
| Ecoregion: | 58b - Western New England Marble Valleys |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 01267 - Williamstown, MA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 11 | 12 | 22 | 32 | 43 | 52 | 56 | 55 | 47 | 36 | 28 | 18 | 34 |
| Avg Max Temp (°F) | 30 | 33 | 42 | 54 | 67 | 75 | 80 | 78 | 70 | 59 | 46 | 35 | 56 |
| Avg Precip (In.) | 2.41 | 1.82 | 2.38 | 3.01 | 3.8 | 3.87 | 4.15 | 4.33 | 3.65 | 3.38 | 3.3 | 2.45 | 38.55 |