Roseau, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -2.5 °C (low) to 9 °C (high). Annual precipitation averages 619.3 Millimeters. Roseau is located in USDA Plant Hardiness Zone 3b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -20.7 °C | -10.3 °C | 18.29 mm |
| February | -19.3 °C | -7.5 °C | 13.97 mm |
| March | -11.3 °C | 0.1 °C | 18.29 mm |
| April | -2.3 °C | 9.5 °C | 32.26 mm |
| May | 4.8 °C | 17.5 °C | 81.03 mm |
| June | 11 °C | 22.8 °C | 112.27 mm |
| July | 13.1 °C | 25.6 °C | 91.95 mm |
| August | 11.5 °C | 24.9 °C | 75.18 mm |
| September | 6.9 °C | 20.1 °C | 73.91 mm |
| October | 0.2 °C | 10.9 °C | 52.83 mm |
| November | -7.6 °C | 1.2 °C | 24.64 mm |
| December | -15.8 °C | -6.7 °C | 24.64 mm |
| Annual | -2.5 °C | 9 °C | 619.26 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 3b : -37.2°C to -34.4°C |
| Plant Hardiness Zone - 2012 | Zone 3a : -40°C to -37.2°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |