Altamont, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.5 °C (low) to 11.6 °C (high). Annual precipitation averages 680 Millimeters. Altamont 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 °C | -6 °C | 17.27 mm |
| February | -13.9 °C | -3.6 °C | 20.57 mm |
| March | -7.2 °C | 3.3 °C | 35.05 mm |
| April | -0.3 °C | 11.8 °C | 67.31 mm |
| May | 7 °C | 18.9 °C | 85.6 mm |
| June | 12.9 °C | 24.2 °C | 107.44 mm |
| July | 15.6 °C | 27.2 °C | 87.63 mm |
| August | 14.2 °C | 26 °C | 78.74 mm |
| September | 9.3 °C | 21.6 °C | 69.6 mm |
| October | 1.9 °C | 13.9 °C | 58.67 mm |
| November | -5.6 °C | 4.6 °C | 28.45 mm |
| December | -12.4 °C | -3.1 °C | 23.62 mm |
| Annual | 0.5 °C | 11.6 °C | 679.95 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |