Custer, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 31.5 °F (low) to 55.8 °F (high). Annual precipitation averages 20.9 Inches. Custer is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.1 - Sep. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.3 °F | 36.7 °F | 0.41 in. |
| February | 13.9 °F | 37.2 °F | 0.69 in. |
| March | 21.2 °F | 45.1 °F | 1.04 in. |
| April | 27.9 °F | 51.7 °F | 2.32 in. |
| May | 37.7 °F | 60.9 °F | 3.68 in. |
| June | 46.9 °F | 71.7 °F | 3.25 in. |
| July | 53.5 °F | 79.7 °F | 3.3 in. |
| August | 51.7 °F | 79.0 °F | 2.26 in. |
| September | 43.2 °F | 70.7 °F | 1.5 in. |
| October | 31.5 °F | 56.0 °F | 1.51 in. |
| November | 21.8 °F | 44.4 °F | 0.56 in. |
| December | 14.7 °F | 36.5 °F | 0.42 in. |
| Annual | 31.5 °F | 55.8 °F | 20.94 in. |
| Average First Frost Date | Sep.1 - Sep. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 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 | Extreme Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |