Ottertail, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.2 °C (low) to 10.7 °C (high). Annual precipitation averages 685.8 Millimeters. Ottertail 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -17.9 °C | -7.7 °C | 16.76 mm |
| February | -16.2 °C | -4.9 °C | 15.75 mm |
| March | -8.6 °C | 2.4 °C | 29.46 mm |
| April | -0.8 °C | 11.3 °C | 54.61 mm |
| May | 6.7 °C | 18.8 °C | 87.88 mm |
| June | 12.8 °C | 24 °C | 115.82 mm |
| July | 15.3 °C | 26.5 °C | 105.92 mm |
| August | 13.8 °C | 25.6 °C | 76.45 mm |
| September | 9.3 °C | 21.2 °C | 71.12 mm |
| October | 1.9 °C | 12.7 °C | 68.33 mm |
| November | -5.8 °C | 3.1 °C | 24.13 mm |
| December | -13.4 °C | -4.4 °C | 19.56 mm |
| Annual | -0.2 °C | 10.7 °C | 685.79 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |