Houlton, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.5 °C (low) to 11.1 °C (high). Annual precipitation averages 1058.2 Millimeters. Houlton is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.2 °C | -4.8 °C | 87.12 mm |
| February | -15.4 °C | -2.9 °C | 67.56 mm |
| March | -8.9 °C | 2.3 °C | 77.98 mm |
| April | -1.6 °C | 9.7 °C | 81.28 mm |
| May | 4.8 °C | 17.8 °C | 84.33 mm |
| June | 9.9 °C | 22.9 °C | 104.14 mm |
| July | 13.1 °C | 25.7 °C | 91.69 mm |
| August | 12.1 °C | 25.1 °C | 85.85 mm |
| September | 7.8 °C | 20.6 °C | 82.3 mm |
| October | 2 °C | 12.9 °C | 99.31 mm |
| November | -3.3 °C | 5.3 °C | 93.98 mm |
| December | -10.7 °C | -1.2 °C | 102.62 mm |
| Annual | -0.5 °C | 11.1 °C | 1058.16 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |