Smithwick, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.1 °C (low) to 16.8 °C (high). Annual precipitation averages 462 Millimeters. Smithwick is located in USDA Plant Hardiness Zone 5a. 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 | -10.6 °C | 3.2 °C | 10.16 mm |
| February | -9.6 °C | 4.8 °C | 14.48 mm |
| March | -4.9 °C | 10.7 °C | 25.65 mm |
| April | -0.3 °C | 15.4 °C | 49.78 mm |
| May | 5.7 °C | 20.5 °C | 83.06 mm |
| June | 11.2 °C | 26.9 °C | 78.74 mm |
| July | 14.8 °C | 31.7 °C | 57.4 mm |
| August | 13.4 °C | 31.2 °C | 45.72 mm |
| September | 7.7 °C | 26.1 °C | 36.58 mm |
| October | 0.8 °C | 17.5 °C | 34.8 mm |
| November | -5.5 °C | 9.8 °C | 13.97 mm |
| December | -9.9 °C | 3.8 °C | 11.68 mm |
| Annual | 1.1 °C | 16.8 °C | 462.02 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |