Mercer, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -1.1 °C (low) to 11.2 °C (high). Annual precipitation averages 454.9 Millimeters. Mercer 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 | -17.2 °C | -6.9 °C | 12.7 mm |
| February | -15.2 °C | -4.4 °C | 11.18 mm |
| March | -8.7 °C | 2.5 °C | 16.76 mm |
| April | -1.7 °C | 11.7 °C | 25.65 mm |
| May | 5.3 °C | 18.9 °C | 66.04 mm |
| June | 11.3 °C | 23.9 °C | 90.17 mm |
| July | 14.1 °C | 27.6 °C | 71.37 mm |
| August | 12.7 °C | 27.4 °C | 50.8 mm |
| September | 7.4 °C | 21.8 °C | 43.94 mm |
| October | 0.3 °C | 12.8 °C | 34.54 mm |
| November | -7.3 °C | 3.1 °C | 16.76 mm |
| December | -13.8 °C | -4.2 °C | 14.99 mm |
| Annual | -1.1 °C | 11.2 °C | 454.9 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 |