Stewartville, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.7 °C (low) to 12.2 °C (high). Annual precipitation averages 884.9 Millimeters. Stewartville is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.3 °C | -5.2 °C | 23.88 mm |
| February | -12.3 °C | -2.8 °C | 25.91 mm |
| March | -5.5 °C | 4.1 °C | 46.23 mm |
| April | 1.3 °C | 12.6 °C | 90.17 mm |
| May | 8.1 °C | 19.6 °C | 115.06 mm |
| June | 13.9 °C | 25.1 °C | 140.21 mm |
| July | 15.8 °C | 26.9 °C | 109.73 mm |
| August | 14.5 °C | 25.7 °C | 106.93 mm |
| September | 9.9 °C | 22.1 °C | 90.68 mm |
| October | 3 °C | 14.6 °C | 62.99 mm |
| November | -3.7 °C | 5.5 °C | 41.91 mm |
| December | -10.3 °C | -2.1 °C | 31.24 mm |
| Annual | 1.7 °C | 12.2 °C | 884.94 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°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 |