Ortley, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.4 °C (low) to 11.6 °C (high). Annual precipitation averages 626.4 Millimeters. Ortley 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 | -16.4 °C | -6.3 °C | 17.02 mm |
| February | -14.4 °C | -3.7 °C | 17.02 mm |
| March | -7.8 °C | 3.1 °C | 27.43 mm |
| April | -0.4 °C | 11.9 °C | 58.42 mm |
| May | 6.9 °C | 19.2 °C | 75.95 mm |
| June | 13 °C | 24.6 °C | 98.81 mm |
| July | 15.6 °C | 27.3 °C | 100.58 mm |
| August | 14.4 °C | 26.6 °C | 67.56 mm |
| September | 9.6 °C | 22.2 °C | 64.01 mm |
| October | 2 °C | 13.8 °C | 59.44 mm |
| November | -5.7 °C | 4.3 °C | 21.08 mm |
| December | -12.6 °C | -3.3 °C | 19.05 mm |
| Annual | 0.4 °C | 11.6 °C | 626.37 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |