Agar, South Dakota has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 0.9 °C (low) to 14 °C (high). Annual precipitation averages 512.8 Millimeters. Agar 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 | -14.3 °C | -3.2 °C | 10.67 mm |
| February | -12.2 °C | -0.7 °C | 16 mm |
| March | -6.4 °C | 6.3 °C | 21.59 mm |
| April | -0.1 °C | 14 °C | 48.01 mm |
| May | 6.6 °C | 20.4 °C | 78.74 mm |
| June | 12.6 °C | 25.9 °C | 89.41 mm |
| July | 15.6 °C | 30.1 °C | 68.58 mm |
| August | 14.6 °C | 29.4 °C | 61.47 mm |
| September | 9.4 °C | 24.6 °C | 44.45 mm |
| October | 1.8 °C | 15.6 °C | 46.48 mm |
| November | -5.4 °C | 6.6 °C | 14.73 mm |
| December | -11.5 °C | -0.9 °C | 12.7 mm |
| Annual | 0.9 °C | 14 °C | 512.83 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 | BSk - Cold Semi-Arid Climate |