Fosston, Minnesota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.8 °C (low) to 9.7 °C (high). Annual precipitation averages 657.6 Millimeters. Fosston 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 | -19.7 °C | -9 °C | 19.3 mm |
| February | -18.3 °C | -6.4 °C | 17.78 mm |
| March | -10.2 °C | 1.2 °C | 24.13 mm |
| April | -1.9 °C | 10.3 °C | 37.34 mm |
| May | 5.4 °C | 18.2 °C | 79.25 mm |
| June | 11.6 °C | 23.3 °C | 118.62 mm |
| July | 13.6 °C | 25.8 °C | 96.52 mm |
| August | 12.1 °C | 25.2 °C | 79.76 mm |
| September | 7.2 °C | 20.3 °C | 77.98 mm |
| October | 0.7 °C | 11.6 °C | 59.18 mm |
| November | -7.3 °C | 1.8 °C | 23.62 mm |
| December | -15.1 °C | -5.7 °C | 24.13 mm |
| Annual | -1.8 °C | 9.7 °C | 657.61 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 |