Monroe, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.2 °C (low) to 12.4 °C (high). Annual precipitation averages 1217.4 Millimeters. Monroe 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.6 °C | -2.5 °C | 94.49 mm |
| February | -12.8 °C | -0.6 °C | 81.79 mm |
| March | -6.8 °C | 4.2 °C | 100.84 mm |
| April | 0.1 °C | 11.3 °C | 108.71 mm |
| May | 6.1 °C | 18.1 °C | 93.98 mm |
| June | 11.2 °C | 23 °C | 106.17 mm |
| July | 14.4 °C | 26.2 °C | 84.07 mm |
| August | 13.6 °C | 25.7 °C | 87.12 mm |
| September | 9.2 °C | 21.3 °C | 98.3 mm |
| October | 3.2 °C | 14.1 °C | 132.59 mm |
| November | -1.9 °C | 7.1 °C | 112.01 mm |
| December | -8.3 °C | 0.8 °C | 117.35 mm |
| Annual | 1.2 °C | 12.4 °C | 1217.42 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |