Chelsea, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 0.1 °C (low) to 12.8 °C (high). Annual precipitation averages 566.9 Millimeters. 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 | -16.3 °C | -5.4 °C | 12.95 mm |
| February | -13.9 °C | -2.3 °C | 16.26 mm |
| March | -7.2 °C | 4.7 °C | 24.13 mm |
| April | -0.4 °C | 13.2 °C | 53.34 mm |
| May | 6.9 °C | 20.3 °C | 84.07 mm |
| June | 13 °C | 25.7 °C | 92.96 mm |
| July | 15.6 °C | 28.6 °C | 83.31 mm |
| August | 13.9 °C | 27.9 °C | 61.47 mm |
| September | 8.6 °C | 23.3 °C | 53.59 mm |
| October | 1.1 °C | 14.9 °C | 51.31 mm |
| November | -6.5 °C | 5.4 °C | 18.03 mm |
| December | -13.1 °C | -2.6 °C | 15.49 mm |
| Annual | 0.1 °C | 12.8 °C | 566.91 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |