Hanover, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.2 °F (low) to 58.5 °F (high). Annual precipitation averages 38.1 Inches. Hanover is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 11.6 °F | 28.6 °F | 1.37 in. |
| February | 15.0 °F | 33.0 °F | 1.63 in. |
| March | 26.1 °F | 45.8 °F | 2.2 in. |
| April | 36.9 °F | 59.1 °F | 3.79 in. |
| May | 48.6 °F | 70.8 °F | 4.34 in. |
| June | 58.8 °F | 80.6 °F | 5.72 in. |
| July | 62.4 °F | 83.7 °F | 4.53 in. |
| August | 60.2 °F | 81.8 °F | 3.88 in. |
| September | 51.7 °F | 75.4 °F | 3.69 in. |
| October | 40.2 °F | 62.4 °F | 2.95 in. |
| November | 28.7 °F | 46.9 °F | 2.27 in. |
| December | 18.0 °F | 34.1 °F | 1.77 in. |
| Annual | 38.2 °F | 58.5 °F | 38.14 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |