Boy River, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.4 °C (low) to 10.3 °C (high). Annual precipitation averages 690.6 Millimeters. Boy River is located in USDA Plant Hardiness Zone 3b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -19.1 °C | -7.9 °C | 18.54 mm |
| February | -17.3 °C | -4.4 °C | 17.53 mm |
| March | -9.7 °C | 2.8 °C | 29.72 mm |
| April | -1.9 °C | 10.7 °C | 49.78 mm |
| May | 5.3 °C | 18.4 °C | 78.49 mm |
| June | 11.2 °C | 23.4 °C | 106.93 mm |
| July | 13.8 °C | 25.9 °C | 107.7 mm |
| August | 12.4 °C | 24.9 °C | 84.33 mm |
| September | 7.8 °C | 20.1 °C | 78.74 mm |
| October | 1.2 °C | 11.6 °C | 65.79 mm |
| November | -6.1 °C | 2.4 °C | 29.97 mm |
| December | -14.1 °C | -4.9 °C | 23.11 mm |
| Annual | -1.4 °C | 10.3 °C | 690.63 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 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 | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |