Chelsea, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.5 °C (low) to 12.3 °C (high). Annual precipitation averages 1016.3 Millimeters. Chelsea is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.5 °C | -2.6 °C | 67.82 mm |
| February | -14.3 °C | -0.9 °C | 55.12 mm |
| March | -8.8 °C | 3.8 °C | 73.66 mm |
| April | -1.7 °C | 11.4 °C | 78.23 mm |
| May | 4.7 °C | 18.9 °C | 84.33 mm |
| June | 9.8 °C | 23.6 °C | 106.17 mm |
| July | 12.6 °C | 26.1 °C | 115.32 mm |
| August | 11.3 °C | 25.3 °C | 98.04 mm |
| September | 7.2 °C | 21.3 °C | 83.06 mm |
| October | 1.3 °C | 13.8 °C | 100.58 mm |
| November | -3.8 °C | 6.8 °C | 73.15 mm |
| December | -10 °C | 0.3 °C | 80.77 mm |
| Annual | -0.5 °C | 12.3 °C | 1016.25 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |