Stephan, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 33 °F (low) to 57.7 °F (high). Annual precipitation averages 20.9 Inches. Stephan 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 | 5.8 °F | 27.0 °F | 0.44 in. |
| February | 9.8 °F | 31.9 °F | 0.62 in. |
| March | 20.4 °F | 44.3 °F | 0.87 in. |
| April | 31.5 °F | 57.6 °F | 2.08 in. |
| May | 43.5 °F | 68.8 °F | 3.17 in. |
| June | 54.5 °F | 79.2 °F | 3.68 in. |
| July | 59.8 °F | 86.4 °F | 2.77 in. |
| August | 57.6 °F | 84.5 °F | 2.26 in. |
| September | 48.1 °F | 76.7 °F | 2.01 in. |
| October | 34.3 °F | 60.7 °F | 1.84 in. |
| November | 20.8 °F | 44.5 °F | 0.59 in. |
| December | 10.4 °F | 31.2 °F | 0.53 in. |
| Annual | 33 °F | 57.7 °F | 20.86 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |