Mahtowa, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.1 °C (low) to 10.6 °C (high). Annual precipitation averages 800.4 Millimeters. Mahtowa is located in USDA Plant Hardiness Zone 4a. 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 | -17.5 °C | -6.8 °C | 21.59 mm |
| February | -15.6 °C | -3.6 °C | 22.35 mm |
| March | -8.9 °C | 3 °C | 35.31 mm |
| April | -1.9 °C | 10.2 °C | 62.99 mm |
| May | 4.2 °C | 17.9 °C | 89.41 mm |
| June | 9.6 °C | 23.1 °C | 115.82 mm |
| July | 13.1 °C | 26.1 °C | 113.79 mm |
| August | 12.3 °C | 25.1 °C | 99.06 mm |
| September | 7.9 °C | 20.3 °C | 86.11 mm |
| October | 1.6 °C | 12.2 °C | 78.49 mm |
| November | -5.4 °C | 3.3 °C | 42.16 mm |
| December | -12.9 °C | -4 °C | 33.27 mm |
| Annual | -1.1 °C | 10.6 °C | 800.35 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 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 |