Fort Thompson, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 1.7 °C (low) to 14.7 °C (high). Annual precipitation averages 524.5 Millimeters. Fort Thompson is located in USDA Plant Hardiness Zone 4b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.8 °C | -1.8 °C | 11.43 mm |
| February | -11.7 °C | 0.9 °C | 14.48 mm |
| March | -5.9 °C | 7.6 °C | 22.86 mm |
| April | 0.5 °C | 14.2 °C | 50.55 mm |
| May | 7.6 °C | 20.6 °C | 78.23 mm |
| June | 13.8 °C | 26.3 °C | 95.25 mm |
| July | 16.9 °C | 30.6 °C | 71.12 mm |
| August | 15.5 °C | 29.4 °C | 63.5 mm |
| September | 10.3 °C | 25.1 °C | 49.28 mm |
| October | 2.3 °C | 16.3 °C | 43.18 mm |
| November | -4.9 °C | 7.4 °C | 12.7 mm |
| December | -10.8 °C | 0.3 °C | 11.94 mm |
| Annual | 1.7 °C | 14.7 °C | 524.52 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |