Grand Isle, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.3 °F (low) to 55.1 °F (high). Annual precipitation averages 36.7 Inches. 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 | 10.3 °F | 27.3 °F | 2.22 in. |
| February | 11.8 °F | 30.1 °F | 1.84 in. |
| March | 21.5 °F | 39.2 °F | 2.25 in. |
| April | 34.4 °F | 53.5 °F | 2.93 in. |
| May | 46.9 °F | 67.3 °F | 3.36 in. |
| June | 56.7 °F | 75.3 °F | 4.25 in. |
| July | 62.0 °F | 80.1 °F | 3.84 in. |
| August | 60.0 °F | 79.4 °F | 3.68 in. |
| September | 52.4 °F | 71.6 °F | 3.28 in. |
| October | 41.2 °F | 58.1 °F | 3.72 in. |
| November | 30.9 °F | 45.6 °F | 2.73 in. |
| December | 19.4 °F | 34.0 °F | 2.62 in. |
| Annual | 37.3 °F | 55.1 °F | 36.72 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 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |