Overly, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -2.8 °C (low) to 9.8 °C (high). Annual precipitation averages 473 Millimeters. Overly 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 | -20.1 °C | -9.2 °C | 13.21 mm |
| February | -18.2 °C | -6.4 °C | 13.21 mm |
| March | -10.8 °C | 0.5 °C | 19.56 mm |
| April | -2.6 °C | 10.8 °C | 23.62 mm |
| May | 4.6 °C | 18.6 °C | 60.71 mm |
| June | 10.7 °C | 23.4 °C | 90.93 mm |
| July | 13 °C | 26.3 °C | 78.49 mm |
| August | 11.4 °C | 26.3 °C | 62.74 mm |
| September | 6 °C | 20.8 °C | 40.64 mm |
| October | -1.3 °C | 11.7 °C | 33.78 mm |
| November | -9.3 °C | 1.4 °C | 19.3 mm |
| December | -16.4 °C | -6.3 °C | 16.76 mm |
| Annual | -2.8 °C | 9.8 °C | 472.95 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |