| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°F | |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F | |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F | |
| Average First Frost Date: | Oct. 11 - Oct. 20 | |
| Average Last Frost Date: | May 11 - May 20 | |
| 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 01860 - Merrimac, MA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 15 | 18 | 26 | 35 | 45 | 54 | 60 | 59 | 51 | 40 | 32 | 21 | 38 |
| Avg Max Temp (°F) | 35 | 37 | 46 | 57 | 68 | 77 | 83 | 81 | 73 | 62 | 50 | 39 | 59 |
| Avg Precip (In.) | 3.99 | 3.29 | 4.08 | 4.29 | 3.62 | 3.66 | 3.52 | 3.36 | 3.88 | 4.21 | 4.49 | 4.06 | 46.47 |