Manteno, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.9 °F (low) to 60.3 °F (high). Annual precipitation averages 40.4 Inches. 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 | 16.2 °F | 31.8 °F | 2.23 in. |
| February | 19.3 °F | 36.0 °F | 1.99 in. |
| March | 28.7 °F | 47.6 °F | 2.41 in. |
| April | 39.0 °F | 60.6 °F | 3.83 in. |
| May | 50.2 °F | 71.7 °F | 4.57 in. |
| June | 60.1 °F | 81.1 °F | 4.79 in. |
| July | 64.1 °F | 84.4 °F | 4.65 in. |
| August | 62.2 °F | 82.8 °F | 4.07 in. |
| September | 54.3 °F | 77.1 °F | 3.4 in. |
| October | 42.4 °F | 64.3 °F | 3.44 in. |
| November | 31.9 °F | 49.5 °F | 2.76 in. |
| December | 22.0 °F | 37.1 °F | 2.25 in. |
| Annual | 40.9 °F | 60.3 °F | 40.39 in. |
| 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 : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |