Chelsea, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 32.2 °F (low) to 55.1 °F (high). Annual precipitation averages 22.3 Inches. Chelsea 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 Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.6 °F | 22.3 °F | 0.51 in. |
| February | 7.0 °F | 27.8 °F | 0.64 in. |
| March | 19.0 °F | 40.4 °F | 0.95 in. |
| April | 31.3 °F | 55.7 °F | 2.1 in. |
| May | 44.4 °F | 68.6 °F | 3.31 in. |
| June | 55.4 °F | 78.2 °F | 3.66 in. |
| July | 60.0 °F | 83.5 °F | 3.28 in. |
| August | 57.1 °F | 82.2 °F | 2.42 in. |
| September | 47.4 °F | 74.0 °F | 2.11 in. |
| October | 33.9 °F | 58.9 °F | 2.02 in. |
| November | 20.3 °F | 41.7 °F | 0.71 in. |
| December | 8.5 °F | 27.4 °F | 0.61 in. |
| Annual | 32.2 °F | 55.1 °F | 22.32 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| 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 4a : -30°F to -25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |