Rothsay, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.3 °C (low) to 10.9 °C (high). Annual precipitation averages 643.1 Millimeters. Rothsay 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 | -17.6 °C | -7.8 °C | 18.29 mm |
| February | -15.6 °C | -5.3 °C | 16.51 mm |
| March | -7.7 °C | 2.1 °C | 27.43 mm |
| April | 0.2 °C | 11.4 °C | 45.97 mm |
| May | 7.4 °C | 19.2 °C | 84.58 mm |
| June | 13.7 °C | 24.4 °C | 107.19 mm |
| July | 15.9 °C | 26.7 °C | 91.95 mm |
| August | 14.6 °C | 26.1 °C | 71.88 mm |
| September | 9.6 °C | 21.6 °C | 72.39 mm |
| October | 2.1 °C | 12.9 °C | 63.75 mm |
| November | -5.7 °C | 3.4 °C | 22.1 mm |
| December | -13.3 °C | -4.3 °C | 21.08 mm |
| Annual | 0.3 °C | 10.9 °C | 643.12 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 |