Altamont, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 32.8 °F (low) to 52.8 °F (high). Annual precipitation averages 26.8 Inches. 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 | 3.2 °F | 21.2 °F | 0.68 in. |
| February | 7.0 °F | 25.6 °F | 0.81 in. |
| March | 19.0 °F | 38.0 °F | 1.38 in. |
| April | 31.5 °F | 53.2 °F | 2.65 in. |
| May | 44.6 °F | 66.1 °F | 3.37 in. |
| June | 55.3 °F | 75.6 °F | 4.23 in. |
| July | 60.0 °F | 80.9 °F | 3.45 in. |
| August | 57.6 °F | 78.8 °F | 3.1 in. |
| September | 48.8 °F | 70.9 °F | 2.74 in. |
| October | 35.4 °F | 57.0 °F | 2.31 in. |
| November | 21.9 °F | 40.2 °F | 1.12 in. |
| December | 9.6 °F | 26.5 °F | 0.93 in. |
| Annual | 32.8 °F | 52.8 °F | 26.77 in. |
| 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 : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |