Letcher, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 35.4 °F (low) to 58 °F (high). Annual precipitation averages 24.6 Inches. Letcher 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 Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.5 °F | 26.9 °F | 0.52 in. |
| February | 11.5 °F | 32.5 °F | 0.69 in. |
| March | 22.3 °F | 44.2 °F | 1.15 in. |
| April | 34.1 °F | 58.4 °F | 2.84 in. |
| May | 46.9 °F | 70.2 °F | 3.52 in. |
| June | 57.9 °F | 80.2 °F | 3.85 in. |
| July | 62.2 °F | 85.7 °F | 2.96 in. |
| August | 59.8 °F | 83.7 °F | 2.9 in. |
| September | 50.6 °F | 76.2 °F | 2.58 in. |
| October | 36.6 °F | 61.4 °F | 2.06 in. |
| November | 23.4 °F | 44.9 °F | 0.88 in. |
| December | 12.4 °F | 31.2 °F | 0.64 in. |
| Annual | 35.4 °F | 58 °F | 24.59 in. |
| 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 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |