Hecla, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 31.6 °F (low) to 53.3 °F (high). Annual precipitation averages 22.9 Inches. Hecla is located in USDA Plant Hardiness Zone 4a. 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 | 1.0 °F | 19.9 °F | 0.52 in. |
| February | 5.3 °F | 25.0 °F | 0.58 in. |
| March | 17.7 °F | 37.7 °F | 0.9 in. |
| April | 31.0 °F | 54.2 °F | 1.74 in. |
| May | 44.4 °F | 67.6 °F | 3.31 in. |
| June | 55.5 °F | 77.0 °F | 3.99 in. |
| July | 59.6 °F | 82.0 °F | 3.6 in. |
| August | 56.7 °F | 80.8 °F | 2.39 in. |
| September | 47.0 °F | 72.5 °F | 2.5 in. |
| October | 33.6 °F | 57.2 °F | 2.09 in. |
| November | 19.9 °F | 39.4 °F | 0.69 in. |
| December | 8.0 °F | 25.8 °F | 0.63 in. |
| Annual | 31.6 °F | 53.3 °F | 22.94 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 4a : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |