Vassalboro, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.9 °C (low) to 12.8 °C (high). Annual precipitation averages 1146.6 Millimeters. Vassalboro is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.3 °C | -1.8 °C | 83.31 mm |
| February | -11.4 °C | -0.1 °C | 71.88 mm |
| March | -5.9 °C | 4.6 °C | 90.68 mm |
| April | 0.5 °C | 11.7 °C | 99.31 mm |
| May | 6.4 °C | 18.4 °C | 87.63 mm |
| June | 11.8 °C | 23.3 °C | 104.39 mm |
| July | 15.1 °C | 26.3 °C | 85.09 mm |
| August | 14.2 °C | 25.8 °C | 89.15 mm |
| September | 9.9 °C | 21.7 °C | 95.76 mm |
| October | 3.9 °C | 14.6 °C | 129.03 mm |
| November | -1.6 °C | 7.7 °C | 105.16 mm |
| December | -7.7 °C | 1.6 °C | 105.16 mm |
| Annual | 1.9 °C | 12.8 °C | 1146.55 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |