Spearfish, South Dakota has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 34.5 °F (low) to 58.9 °F (high). Annual precipitation averages 24.1 Inches. Spearfish is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.7 °F | 36.7 °F | 0.73 in. |
| February | 15.8 °F | 37.8 °F | 1.03 in. |
| March | 23.6 °F | 47.2 °F | 1.28 in. |
| April | 31.7 °F | 55.7 °F | 2.63 in. |
| May | 41.7 °F | 65.5 °F | 4.15 in. |
| June | 51.2 °F | 76.2 °F | 3.91 in. |
| July | 57.8 °F | 84.9 °F | 2.45 in. |
| August | 55.8 °F | 84.1 °F | 1.94 in. |
| September | 46.7 °F | 74.5 °F | 1.65 in. |
| October | 34.8 °F | 59.6 °F | 2.22 in. |
| November | 24.3 °F | 46.9 °F | 0.99 in. |
| December | 16.3 °F | 37.5 °F | 1.15 in. |
| Annual | 34.5 °F | 58.9 °F | 24.13 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |