South Ashburnham, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.7 °F (low) to 56.3 °F (high). Annual precipitation averages 48.4 Inches. South Ashburnham is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.5 °F | 31.0 °F | 3.59 in. |
| February | 13.9 °F | 34.1 °F | 3.26 in. |
| March | 21.6 °F | 41.8 °F | 4.26 in. |
| April | 32.9 °F | 55.0 °F | 3.95 in. |
| May | 43.8 °F | 66.4 °F | 3.81 in. |
| June | 52.9 °F | 74.9 °F | 4.27 in. |
| July | 58.4 °F | 80.1 °F | 4.07 in. |
| August | 56.7 °F | 78.6 °F | 4.1 in. |
| September | 49.3 °F | 71.4 °F | 4.11 in. |
| October | 38.0 °F | 58.4 °F | 4.94 in. |
| November | 28.8 °F | 47.0 °F | 3.76 in. |
| December | 19.5 °F | 36.4 °F | 4.3 in. |
| Annual | 35.7 °F | 56.3 °F | 48.42 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |