Manteno, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 15.7 °C (high). Annual precipitation averages 1025.9 Millimeters. Manteno is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.8 °C | -0.1 °C | 56.64 mm |
| February | -7.1 °C | 2.2 °C | 50.55 mm |
| March | -1.8 °C | 8.7 °C | 61.21 mm |
| April | 3.9 °C | 15.9 °C | 97.28 mm |
| May | 10.1 °C | 22.1 °C | 116.08 mm |
| June | 15.6 °C | 27.3 °C | 121.67 mm |
| July | 17.8 °C | 29.1 °C | 118.11 mm |
| August | 16.8 °C | 28.2 °C | 103.38 mm |
| September | 12.4 °C | 25.1 °C | 86.36 mm |
| October | 5.8 °C | 17.9 °C | 87.38 mm |
| November | -0.1 °C | 9.7 °C | 70.1 mm |
| December | -5.6 °C | 2.8 °C | 57.15 mm |
| Annual | 4.9 °C | 15.7 °C | 1025.91 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 |