Bismarck, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.5 °C (low) to 12.5 °C (high). Annual precipitation averages 484.4 Millimeters. Bismarck 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 | -16.3 °C | -5.1 °C | 12.95 mm |
| February | -13.8 °C | -2.6 °C | 12.45 mm |
| March | -7.7 °C | 4.4 °C | 18.8 mm |
| April | -1.1 °C | 12.8 °C | 30.73 mm |
| May | 5.8 °C | 19.7 °C | 66.29 mm |
| June | 11.6 °C | 24.9 °C | 85.6 mm |
| July | 14.4 °C | 28.6 °C | 83.82 mm |
| August | 13.1 °C | 28.2 °C | 59.44 mm |
| September | 7.8 °C | 22.8 °C | 44.45 mm |
| October | 0.5 °C | 13.9 °C | 35.05 mm |
| November | -6.8 °C | 4.7 °C | 18.8 mm |
| December | -12.9 °C | -2.3 °C | 16 mm |
| Annual | -0.5 °C | 12.5 °C | 484.38 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 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |