Webster, South Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 0.7 °C (low) to 11.4 °C (high). Annual precipitation averages 638.3 Millimeters. Webster 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 | -16.3 °C | -6.4 °C | 19.56 mm |
| February | -14.2 °C | -3.7 °C | 18.54 mm |
| March | -7.6 °C | 2.9 °C | 27.69 mm |
| April | -0.2 °C | 11.5 °C | 59.44 mm |
| May | 7.3 °C | 19 °C | 81.03 mm |
| June | 13.4 °C | 24.3 °C | 101.35 mm |
| July | 16.1 °C | 27.1 °C | 100.08 mm |
| August | 15 °C | 26.3 °C | 67.82 mm |
| September | 10.1 °C | 21.9 °C | 63.75 mm |
| October | 2.3 °C | 13.4 °C | 59.94 mm |
| November | -5.5 °C | 4 °C | 16.51 mm |
| December | -12.3 °C | -3.4 °C | 22.61 mm |
| Annual | 0.7 °C | 11.4 °C | 638.32 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 |