Calais, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.6 °F (low) to 54.3 °F (high). Annual precipitation averages 47.6 Inches. Calais is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.7 °F | 28.3 °F | 4.06 in. |
| February | 9.9 °F | 31.2 °F | 3.25 in. |
| March | 19.9 °F | 39.6 °F | 3.96 in. |
| April | 31.3 °F | 51.3 °F | 3.72 in. |
| May | 41.2 °F | 63.2 °F | 3.79 in. |
| June | 50.5 °F | 72.6 °F | 3.69 in. |
| July | 56.4 °F | 78.6 °F | 3.41 in. |
| August | 54.7 °F | 78.3 °F | 3.29 in. |
| September | 47.4 °F | 70.5 °F | 3.54 in. |
| October | 37.6 °F | 57.9 °F | 5.2 in. |
| November | 28.8 °F | 45.8 °F | 4.8 in. |
| December | 17.3 °F | 34.6 °F | 4.86 in. |
| Annual | 33.6 °F | 54.3 °F | 47.57 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 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 |