South Heart, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.9 °C (low) to 12.6 °C (high). Annual precipitation averages 420.9 Millimeters. South Heart 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 | -15.1 °C | -3.7 °C | 8.89 mm |
| February | -13.1 °C | -1.2 °C | 10.92 mm |
| March | -7.7 °C | 5.1 °C | 18.03 mm |
| April | -1.8 °C | 12.3 °C | 29.21 mm |
| May | 4.6 °C | 18.6 °C | 64.26 mm |
| June | 10.2 °C | 23.8 °C | 79.76 mm |
| July | 13.2 °C | 28.3 °C | 64.77 mm |
| August | 12 °C | 28.4 °C | 40.64 mm |
| September | 6.7 °C | 22.7 °C | 46.23 mm |
| October | -0.4 °C | 13.6 °C | 34.29 mm |
| November | -7.2 °C | 4.8 °C | 13.46 mm |
| December | -12.7 °C | -1.4 °C | 10.41 mm |
| Annual | -0.9 °C | 12.6 °C | 420.87 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |