Erwin, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 33.8 °F (low) to 53.7 °F (high). Annual precipitation averages 25.3 Inches. 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 | 4.2 °F | 22.0 °F | 0.56 in. |
| February | 8.0 °F | 27.0 °F | 0.68 in. |
| March | 19.9 °F | 39.1 °F | 1.11 in. |
| April | 32.6 °F | 54.4 °F | 2.43 in. |
| May | 45.4 °F | 66.9 °F | 3.38 in. |
| June | 56.2 °F | 76.6 °F | 4.25 in. |
| July | 61.0 °F | 81.5 °F | 3.4 in. |
| August | 58.4 °F | 79.4 °F | 3.01 in. |
| September | 49.9 °F | 71.9 °F | 2.73 in. |
| October | 36.0 °F | 57.3 °F | 2.19 in. |
| November | 22.7 °F | 40.9 °F | 0.85 in. |
| December | 10.9 °F | 27.0 °F | 0.69 in. |
| Annual | 33.8 °F | 53.7 °F | 25.28 in. |
| 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 : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |