Fort Thompson, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 34.9 °F (low) to 58.5 °F (high). Annual precipitation averages 20.7 Inches. 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 | 7.1 °F | 28.8 °F | 0.45 in. |
| February | 10.9 °F | 33.7 °F | 0.57 in. |
| March | 21.3 °F | 45.6 °F | 0.9 in. |
| April | 32.9 °F | 57.6 °F | 1.99 in. |
| May | 45.6 °F | 69.0 °F | 3.08 in. |
| June | 56.8 °F | 79.4 °F | 3.75 in. |
| July | 62.4 °F | 87.0 °F | 2.8 in. |
| August | 59.9 °F | 85.0 °F | 2.5 in. |
| September | 50.5 °F | 77.1 °F | 1.94 in. |
| October | 36.1 °F | 61.3 °F | 1.7 in. |
| November | 23.1 °F | 45.3 °F | 0.5 in. |
| December | 12.5 °F | 32.5 °F | 0.47 in. |
| Annual | 34.9 °F | 58.5 °F | 20.65 in. |
| 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 : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |