Goodwin, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Annual precipitation averages 664.5 Millimeters. Goodwin is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.5 °C | -6.3 °C | 17.02 mm |
| February | -14.4 °C | -3.8 °C | 18.8 mm |
| March | -7.7 °C | 3.2 °C | 32.77 mm |
| April | -0.7 °C | 11.8 °C | 64.26 mm |
| May | 6.5 °C | 18.8 °C | 83.57 mm |
| June | 12.4 °C | 24.1 °C | 106.43 mm |
| July | 15.2 °C | 27.3 °C | 88.65 mm |
| August | 13.8 °C | 26.2 °C | 77.98 mm |
| September | 8.9 °C | 21.7 °C | 70.61 mm |
| October | 1.4 °C | 13.6 °C | 57.4 mm |
| November | -6.2 °C | 4.3 °C | 25.91 mm |
| December | -12.9 °C | -3.3 °C | 21.08 mm |
| Annual | -0 °C | 11.5 °C | 664.48 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |