Erwin, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 1 °C (low) to 12 °C (high). Annual precipitation averages 642.1 Millimeters. Erwin 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 | -15.4 °C | -5.6 °C | 14.22 mm |
| February | -13.3 °C | -2.8 °C | 17.27 mm |
| March | -6.7 °C | 3.9 °C | 28.19 mm |
| April | 0.3 °C | 12.4 °C | 61.72 mm |
| May | 7.4 °C | 19.4 °C | 85.85 mm |
| June | 13.4 °C | 24.8 °C | 107.95 mm |
| July | 16.1 °C | 27.5 °C | 86.36 mm |
| August | 14.7 °C | 26.3 °C | 76.45 mm |
| September | 9.9 °C | 22.2 °C | 69.34 mm |
| October | 2.2 °C | 14.1 °C | 55.63 mm |
| November | -5.2 °C | 4.9 °C | 21.59 mm |
| December | -11.7 °C | -2.8 °C | 17.53 mm |
| Annual | 1 °C | 12 °C | 642.1 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |