Forest River, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.2 °C (low) to 10 °C (high). Annual precipitation averages 548.9 Millimeters. Forest River is located in USDA Plant Hardiness Zone 4a. 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 | -19.1 °C | -9.6 °C | 13.72 mm |
| February | -16.9 °C | -6.7 °C | 13.21 mm |
| March | -9.4 °C | 0.3 °C | 21.34 mm |
| April | -1 °C | 10.5 °C | 27.43 mm |
| May | 6 °C | 18.8 °C | 79.5 mm |
| June | 12.4 °C | 24.1 °C | 98.81 mm |
| July | 14.4 °C | 26.6 °C | 81.03 mm |
| August | 12.8 °C | 26.3 °C | 71.37 mm |
| September | 7.8 °C | 21.3 °C | 56.64 mm |
| October | 1 °C | 12.3 °C | 44.96 mm |
| November | -7.2 °C | 1.9 °C | 21.84 mm |
| December | -14.7 °C | -6.2 °C | 19.05 mm |
| Annual | -1.2 °C | 10 °C | 548.9 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| 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 |