Webster, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4 °C (low) to 15.3 °C (high). Annual precipitation averages 959.9 Millimeters. Webster is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.8 °C | -1.3 °C | 30.48 mm |
| February | -8.8 °C | 1.3 °C | 37.08 mm |
| March | -2.8 °C | 8.6 °C | 56.64 mm |
| April | 3.4 °C | 15.9 °C | 96.52 mm |
| May | 10.2 °C | 21.8 °C | 128.02 mm |
| June | 16 °C | 27.1 °C | 134.37 mm |
| July | 17.8 °C | 29.2 °C | 105.16 mm |
| August | 16.3 °C | 28.2 °C | 115.06 mm |
| September | 11.3 °C | 24.6 °C | 88.9 mm |
| October | 4.7 °C | 17.4 °C | 73.15 mm |
| November | -1.8 °C | 8.9 °C | 54.1 mm |
| December | -7.4 °C | 1.7 °C | 40.39 mm |
| Annual | 4 °C | 15.3 °C | 959.87 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |