Flandreau, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 0.8 °C (low) to 12.4 °C (high). Annual precipitation averages 706.6 Millimeters. Flandreau 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 | -15.3 °C | -5 °C | 14.22 mm |
| February | -13.2 °C | -2.3 °C | 19.3 mm |
| March | -6.5 °C | 4.5 °C | 35.05 mm |
| April | 0.2 °C | 12.5 °C | 68.58 mm |
| May | 7.4 °C | 19.5 °C | 94.74 mm |
| June | 13.9 °C | 25.2 °C | 114.05 mm |
| July | 16.1 °C | 27.6 °C | 90.17 mm |
| August | 14.2 °C | 26.2 °C | 87.88 mm |
| September | 9.2 °C | 22.4 °C | 78.49 mm |
| October | 1.7 °C | 14.6 °C | 55.37 mm |
| November | -5.7 °C | 5.5 °C | 26.67 mm |
| December | -12 °C | -2.3 °C | 22.1 mm |
| Annual | 0.8 °C | 12.4 °C | 706.62 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 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 |