Bristol, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 39.4 °F (low) to 53.6 °F (high). Annual precipitation averages 49.3 Inches. Bristol 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 18.9 °F | 32.3 °F | 3.96 in. |
| February | 19.6 °F | 33.9 °F | 3.61 in. |
| March | 26.4 °F | 40.0 °F | 4.49 in. |
| April | 35.3 °F | 50.2 °F | 4.37 in. |
| May | 44.3 °F | 59.9 °F | 3.69 in. |
| June | 53.0 °F | 68.4 °F | 4.24 in. |
| July | 58.7 °F | 74.1 °F | 3.4 in. |
| August | 58.6 °F | 74.2 °F | 3.09 in. |
| September | 53.1 °F | 67.8 °F | 4.08 in. |
| October | 44.1 °F | 57.0 °F | 5.11 in. |
| November | 35.1 °F | 47.4 °F | 4.49 in. |
| December | 25.4 °F | 38.1 °F | 4.79 in. |
| Annual | 39.4 °F | 53.6 °F | 49.32 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| 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 |