Guilford, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 31.8 °F (low) to 53.4 °F (high). Annual precipitation averages 46.5 Inches. Guilford 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 Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 5.0 °F | 25.7 °F | 3.47 in. |
| February | 6.2 °F | 29.3 °F | 2.84 in. |
| March | 17.1 °F | 38.5 °F | 3.53 in. |
| April | 29.3 °F | 51.5 °F | 3.69 in. |
| May | 40.6 °F | 64.6 °F | 3.78 in. |
| June | 50.5 °F | 73.1 °F | 4.69 in. |
| July | 56.1 °F | 78.7 °F | 3.8 in. |
| August | 54.2 °F | 77.6 °F | 3.63 in. |
| September | 46.2 °F | 70.0 °F | 3.79 in. |
| October | 35.6 °F | 56.4 °F | 5.04 in. |
| November | 26.1 °F | 43.7 °F | 4.16 in. |
| December | 14.3 °F | 32.2 °F | 4.06 in. |
| Annual | 31.8 °F | 53.4 °F | 46.48 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |