Manhattan, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.3 °F (low) to 60.3 °F (high). Annual precipitation averages 40 Inches. 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 | 16.6 °F | 32.0 °F | 2.14 in. |
| February | 19.5 °F | 35.9 °F | 2.09 in. |
| March | 29.1 °F | 47.5 °F | 2.38 in. |
| April | 39.6 °F | 60.6 °F | 3.87 in. |
| May | 50.2 °F | 71.5 °F | 4.64 in. |
| June | 60.2 °F | 81.0 °F | 4.63 in. |
| July | 64.4 °F | 84.7 °F | 4.65 in. |
| August | 62.9 °F | 82.9 °F | 4.11 in. |
| September | 55.4 °F | 77.0 °F | 3.45 in. |
| October | 43.1 °F | 63.8 °F | 3.33 in. |
| November | 32.3 °F | 49.5 °F | 2.51 in. |
| December | 22.3 °F | 37.0 °F | 2.19 in. |
| Annual | 41.3 °F | 60.3 °F | 39.99 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 6a : -10°F to -5°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 |