Guilford, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.1 °C (low) to 11.9 °C (high). Annual precipitation averages 1180.6 Millimeters. 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 | -15 °C | -3.5 °C | 88.14 mm |
| February | -14.3 °C | -1.5 °C | 72.14 mm |
| March | -8.3 °C | 3.6 °C | 89.66 mm |
| April | -1.5 °C | 10.8 °C | 93.73 mm |
| May | 4.8 °C | 18.1 °C | 96.01 mm |
| June | 10.3 °C | 22.8 °C | 119.13 mm |
| July | 13.4 °C | 25.9 °C | 96.52 mm |
| August | 12.3 °C | 25.3 °C | 92.2 mm |
| September | 7.9 °C | 21.1 °C | 96.27 mm |
| October | 2 °C | 13.6 °C | 128.02 mm |
| November | -3.3 °C | 6.5 °C | 105.66 mm |
| December | -9.8 °C | 0.1 °C | 103.12 mm |
| Annual | -0.1 °C | 11.9 °C | 1180.6 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |