Hermosa, South Dakota has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 2.1 °C (low) to 15.2 °C (high). Annual precipitation averages 458 Millimeters. Hermosa is located in USDA Plant Hardiness Zone 5a. 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 | -9.4 °C | 2.8 °C | 6.35 mm |
| February | -8.8 °C | 3.6 °C | 11.18 mm |
| March | -4.3 °C | 8.9 °C | 19.05 mm |
| April | 0.3 °C | 13.2 °C | 50.55 mm |
| May | 6.2 °C | 18.3 °C | 85.34 mm |
| June | 11.8 °C | 24.7 °C | 85.85 mm |
| July | 15.6 °C | 29.4 °C | 61.47 mm |
| August | 14.4 °C | 28.8 °C | 50.04 mm |
| September | 9.3 °C | 23.9 °C | 37.59 mm |
| October | 2.3 °C | 15.9 °C | 32.77 mm |
| November | -3.6 °C | 8.9 °C | 9.91 mm |
| December | -8.4 °C | 3.5 °C | 7.87 mm |
| Annual | 2.1 °C | 15.2 °C | 457.97 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |