Sinai, South Dakota has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 1.1 °C (low) to 12.5 °C (high). Annual precipitation averages 669.3 Millimeters. Sinai 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 Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -15 °C | -4.9 °C | 14.73 mm |
| February | -12.6 °C | -2.2 °C | 18.03 mm |
| March | -6.3 °C | 4.4 °C | 30.99 mm |
| April | 0.5 °C | 12.8 °C | 65.02 mm |
| May | 7.6 °C | 19.7 °C | 92.71 mm |
| June | 13.6 °C | 25.2 °C | 106.93 mm |
| July | 15.9 °C | 27.8 °C | 86.87 mm |
| August | 14.6 °C | 26.4 °C | 81.79 mm |
| September | 9.8 °C | 22.6 °C | 73.41 mm |
| October | 2.2 °C | 14.7 °C | 53.85 mm |
| November | -5.2 °C | 5.4 °C | 25.15 mm |
| December | -11.7 °C | -2.2 °C | 19.81 mm |
| Annual | 1.1 °C | 12.5 °C | 669.29 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| 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 | Dfa - Humid Continental Hot Summers With Year Around Precipitation |