Thomaston, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 36.7 °F (low) to 54.2 °F (high). Annual precipitation averages 51.4 Inches. Thomaston is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.6 °F | 30.7 °F | 4.5 in. |
| February | 15.1 °F | 33.0 °F | 3.78 in. |
| March | 23.3 °F | 40.2 °F | 4.77 in. |
| April | 33.7 °F | 51.4 °F | 4.71 in. |
| May | 43.3 °F | 61.7 °F | 3.76 in. |
| June | 52.4 °F | 70.4 °F | 4.04 in. |
| July | 58.4 °F | 76.4 °F | 3.26 in. |
| August | 57.5 °F | 75.9 °F | 3.0 in. |
| September | 50.7 °F | 69.2 °F | 4.44 in. |
| October | 40.3 °F | 57.6 °F | 5.27 in. |
| November | 31.0 °F | 46.9 °F | 4.89 in. |
| December | 20.8 °F | 36.6 °F | 4.97 in. |
| Annual | 36.7 °F | 54.2 °F | 51.39 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |