Custer, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from -0.3 °C (low) to 13.2 °C (high). Annual precipitation averages 531.9 Millimeters. 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 | -9.8 °C | 2.6 °C | 10.41 mm |
| February | -10.1 °C | 2.9 °C | 17.53 mm |
| March | -6 °C | 7.3 °C | 26.42 mm |
| April | -2.3 °C | 10.9 °C | 58.93 mm |
| May | 3.2 °C | 16.1 °C | 93.47 mm |
| June | 8.3 °C | 22.1 °C | 82.55 mm |
| July | 11.9 °C | 26.5 °C | 83.82 mm |
| August | 10.9 °C | 26.1 °C | 57.4 mm |
| September | 6.2 °C | 21.5 °C | 38.1 mm |
| October | -0.3 °C | 13.3 °C | 38.35 mm |
| November | -5.7 °C | 6.9 °C | 14.22 mm |
| December | -9.6 °C | 2.5 °C | 10.67 mm |
| Annual | -0.3 °C | 13.2 °C | 531.87 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |