Grand Isle, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.9 °C (low) to 12.8 °C (high). Annual precipitation averages 932.7 Millimeters. Grand Isle is located in USDA Plant Hardiness Zone 5a. 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 | -12.1 °C | -2.6 °C | 56.39 mm |
| February | -11.2 °C | -1.1 °C | 46.74 mm |
| March | -5.8 °C | 4 °C | 57.15 mm |
| April | 1.3 °C | 11.9 °C | 74.42 mm |
| May | 8.3 °C | 19.6 °C | 85.34 mm |
| June | 13.7 °C | 24.1 °C | 107.95 mm |
| July | 16.7 °C | 26.7 °C | 97.54 mm |
| August | 15.6 °C | 26.3 °C | 93.47 mm |
| September | 11.3 °C | 22 °C | 83.31 mm |
| October | 5.1 °C | 14.5 °C | 94.49 mm |
| November | -0.6 °C | 7.6 °C | 69.34 mm |
| December | -7 °C | 1.1 °C | 66.55 mm |
| Annual | 2.9 °C | 12.8 °C | 932.69 mm |
| 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |