Harrison, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.4 °C (low) to 15.3 °C (high). Annual precipitation averages 636 Millimeters. Harrison is located in USDA Plant Hardiness Zone 5a. 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 | -12.3 °C | -1.1 °C | 13.72 mm |
| February | -10.2 °C | 1.8 °C | 18.54 mm |
| March | -4.7 °C | 8.3 °C | 29.97 mm |
| April | 1.4 °C | 15 °C | 74.42 mm |
| May | 8.1 °C | 21.4 °C | 92.96 mm |
| June | 14.2 °C | 27.1 °C | 97.28 mm |
| July | 17 °C | 30.7 °C | 75.95 mm |
| August | 15.8 °C | 29.5 °C | 74.17 mm |
| September | 10.4 °C | 25.2 °C | 67.06 mm |
| October | 2.9 °C | 16.8 °C | 52.83 mm |
| November | -4.3 °C | 8.2 °C | 22.1 mm |
| December | -9.9 °C | 0.8 °C | 17.02 mm |
| Annual | 2.4 °C | 15.3 °C | 636.02 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 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 | Dfa - Humid Continental Hot Summers With Year Around Precipitation |