Mentor, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.5 °C (low) to 9.6 °C (high). Annual precipitation averages 620.3 Millimeters. Mentor is located in USDA Plant Hardiness Zone 4a. 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 | -19.4 °C | -9.4 °C | 17.53 mm |
| February | -17.9 °C | -6.9 °C | 16.26 mm |
| March | -9.8 °C | 0.8 °C | 23.37 mm |
| April | -1.4 °C | 10.2 °C | 34.29 mm |
| May | 5.8 °C | 18.2 °C | 79.5 mm |
| June | 12 °C | 23.3 °C | 107.7 mm |
| July | 13.9 °C | 25.8 °C | 86.87 mm |
| August | 12.5 °C | 25.4 °C | 78.74 mm |
| September | 7.6 °C | 20.4 °C | 74.93 mm |
| October | 0.8 °C | 11.7 °C | 56.39 mm |
| November | -7.1 °C | 1.8 °C | 22.86 mm |
| December | -15 °C | -6 °C | 21.84 mm |
| Annual | -1.5 °C | 9.6 °C | 620.28 mm |
| 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 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |