Gary, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1 °C (low) to 12.4 °C (high). Annual precipitation averages 690.6 Millimeters. Gary 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 | -15.4 °C | -5.3 °C | 17.78 mm |
| February | -13.3 °C | -2.8 °C | 20.83 mm |
| March | -6.6 °C | 3.8 °C | 36.83 mm |
| April | 0.3 °C | 12.5 °C | 71.12 mm |
| May | 7.6 °C | 19.8 °C | 86.87 mm |
| June | 13.6 °C | 25.3 °C | 106.17 mm |
| July | 15.9 °C | 28 °C | 85.85 mm |
| August | 14.6 °C | 26.7 °C | 81.79 mm |
| September | 9.7 °C | 22.6 °C | 71.63 mm |
| October | 2.3 °C | 14.7 °C | 56.9 mm |
| November | -5 °C | 5.3 °C | 30.23 mm |
| December | -11.7 °C | -2.4 °C | 24.64 mm |
| Annual | 1 °C | 12.4 °C | 690.64 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 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |