Manhattan, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.2 °C (low) to 15.7 °C (high). Annual precipitation averages 1015.8 Millimeters. Manhattan is located in USDA Plant Hardiness Zone 6a. 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 | -8.6 °C | 0 °C | 54.36 mm |
| February | -6.9 °C | 2.2 °C | 53.09 mm |
| March | -1.6 °C | 8.6 °C | 60.45 mm |
| April | 4.2 °C | 15.9 °C | 98.3 mm |
| May | 10.1 °C | 21.9 °C | 117.86 mm |
| June | 15.7 °C | 27.2 °C | 117.6 mm |
| July | 18 °C | 29.3 °C | 118.11 mm |
| August | 17.2 °C | 28.3 °C | 104.39 mm |
| September | 13 °C | 25 °C | 87.63 mm |
| October | 6.2 °C | 17.7 °C | 84.58 mm |
| November | 0.2 °C | 9.7 °C | 63.75 mm |
| December | -5.4 °C | 2.8 °C | 55.63 mm |
| Annual | 5.2 °C | 15.7 °C | 1015.75 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 6a : -23.3°C to -20.6°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 |