Quincy, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.5 °C (low) to 17.4 °C (high). Annual precipitation averages 996.4 Millimeters. Quincy is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.4 °C | 1.7 °C | 45.21 mm |
| February | -5.3 °C | 4.6 °C | 52.58 mm |
| March | -0.2 °C | 11 °C | 66.29 mm |
| April | 6 °C | 18.1 °C | 102.36 mm |
| May | 12.2 °C | 23.4 °C | 125.73 mm |
| June | 17.6 °C | 28.4 °C | 118.62 mm |
| July | 19.4 °C | 30.7 °C | 99.06 mm |
| August | 18.3 °C | 29.8 °C | 99.06 mm |
| September | 13.6 °C | 26.1 °C | 89.66 mm |
| October | 7.2 °C | 19.2 °C | 80.77 mm |
| November | 0.9 °C | 11.2 °C | 67.31 mm |
| December | -4.4 °C | 4.3 °C | 49.78 mm |
| Annual | 6.5 °C | 17.4 °C | 996.43 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |