Rockham, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 0.5 °C (low) to 13.1 °C (high). Annual precipitation averages 560.3 Millimeters. Rockham is located in USDA Plant Hardiness Zone 4b. 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 | -15.7 °C | -4.9 °C | 10.41 mm |
| February | -13.4 °C | -2 °C | 17.27 mm |
| March | -6.8 °C | 5.1 °C | 25.15 mm |
| April | -0.2 °C | 13.4 °C | 53.34 mm |
| May | 7.1 °C | 20.3 °C | 81.79 mm |
| June | 13.1 °C | 25.8 °C | 92.46 mm |
| July | 15.8 °C | 29 °C | 85.09 mm |
| August | 14.3 °C | 28.1 °C | 60.45 mm |
| September | 8.9 °C | 23.5 °C | 55.12 mm |
| October | 1.4 °C | 14.9 °C | 48.51 mm |
| November | -6.2 °C | 5.8 °C | 17.02 mm |
| December | -12.4 °C | -2.1 °C | 13.72 mm |
| Annual | 0.5 °C | 13.1 °C | 560.33 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |