Roy Lake, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.2 °C (low) to 9.9 °C (high). Annual precipitation averages 658.6 Millimeters. Roy Lake is located in USDA Plant Hardiness Zone 3b. 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 | -19.4 °C | -8.2 °C | 16.51 mm |
| February | -17.7 °C | -5.3 °C | 16 mm |
| March | -9.8 °C | 1.9 °C | 26.92 mm |
| April | -1.9 °C | 10.4 °C | 41.4 mm |
| May | 5.8 °C | 18 °C | 78.74 mm |
| June | 11.9 °C | 23.2 °C | 115.32 mm |
| July | 14.4 °C | 26 °C | 99.57 mm |
| August | 13.1 °C | 24.9 °C | 74.93 mm |
| September | 8.3 °C | 20.1 °C | 75.18 mm |
| October | 1.4 °C | 11.4 °C | 65.79 mm |
| November | -6.6 °C | 2.1 °C | 27.94 mm |
| December | -14.2 °C | -5.2 °C | 20.32 mm |
| Annual | -1.2 °C | 9.9 °C | 658.62 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 3b : -37.2°C to -34.4°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 |