Iroquois, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 34.4 °F (low) to 56.7 °F (high). Annual precipitation averages 23.9 Inches. Iroquois 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 | 5.9 °F | 25.1 °F | 0.55 in. |
| February | 10.0 °F | 30.5 °F | 0.68 in. |
| March | 21.3 °F | 42.6 °F | 1.07 in. |
| April | 33.2 °F | 57.3 °F | 2.45 in. |
| May | 45.9 °F | 69.3 °F | 3.1 in. |
| June | 56.9 °F | 79.3 °F | 3.81 in. |
| July | 61.3 °F | 84.8 °F | 3.25 in. |
| August | 59.0 °F | 82.8 °F | 2.93 in. |
| September | 50.0 °F | 75.1 °F | 2.48 in. |
| October | 35.9 °F | 60.3 °F | 2.0 in. |
| November | 22.4 °F | 43.6 °F | 0.83 in. |
| December | 11.2 °F | 29.9 °F | 0.7 in. |
| Annual | 34.4 °F | 56.7 °F | 23.85 in. |
| 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 : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |