Smithwick, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.9 °F (low) to 62.3 °F (high). Annual precipitation averages 18.2 Inches. 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 | 13.0 °F | 37.8 °F | 0.4 in. |
| February | 14.7 °F | 40.7 °F | 0.57 in. |
| March | 23.2 °F | 51.3 °F | 1.01 in. |
| April | 31.4 °F | 59.7 °F | 1.96 in. |
| May | 42.3 °F | 68.9 °F | 3.27 in. |
| June | 52.2 °F | 80.5 °F | 3.1 in. |
| July | 58.6 °F | 89.0 °F | 2.26 in. |
| August | 56.1 °F | 88.1 °F | 1.8 in. |
| September | 45.8 °F | 79.0 °F | 1.44 in. |
| October | 33.4 °F | 63.5 °F | 1.37 in. |
| November | 22.1 °F | 49.6 °F | 0.55 in. |
| December | 14.1 °F | 38.9 °F | 0.46 in. |
| Annual | 33.9 °F | 62.3 °F | 18.19 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |