Waterman, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 14.6 °C (high). Annual precipitation averages 953.5 Millimeters. Waterman 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 | -10.4 °C | -1.8 °C | 44.2 mm |
| February | -8.6 °C | 0.6 °C | 43.94 mm |
| March | -3 °C | 7.5 °C | 57.66 mm |
| April | 2.8 °C | 15 °C | 91.69 mm |
| May | 9.4 °C | 21.3 °C | 123.95 mm |
| June | 14.9 °C | 26.6 °C | 117.35 mm |
| July | 16.8 °C | 28.3 °C | 98.55 mm |
| August | 15.6 °C | 27.2 °C | 97.79 mm |
| September | 10.9 °C | 24.1 °C | 87.88 mm |
| October | 4.4 °C | 16.9 °C | 78.23 mm |
| November | -1.3 °C | 8.5 °C | 61.21 mm |
| December | -7.1 °C | 1.3 °C | 51.05 mm |
| Annual | 3.7 °C | 14.6 °C | 953.5 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 |