Garretson, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 1.6 °C (low) to 13 °C (high). Annual precipitation averages 728.7 Millimeters. Garretson is located in USDA Plant Hardiness Zone 5a. 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 | -14.3 °C | -4.3 °C | 17.27 mm |
| February | -12 °C | -1.7 °C | 21.84 mm |
| March | -5.6 °C | 5.3 °C | 36.83 mm |
| April | 0.9 °C | 13.4 °C | 73.15 mm |
| May | 8.1 °C | 20.2 °C | 95.5 mm |
| June | 14.4 °C | 25.7 °C | 114.05 mm |
| July | 16.4 °C | 28.1 °C | 88.65 mm |
| August | 14.8 °C | 26.8 °C | 86.11 mm |
| September | 9.8 °C | 23.1 °C | 80.01 mm |
| October | 2.6 °C | 15.3 °C | 58.42 mm |
| November | -4.9 °C | 6.2 °C | 32.26 mm |
| December | -11.2 °C | -1.7 °C | 24.64 mm |
| Annual | 1.6 °C | 13 °C | 728.73 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |