Annapolis, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.1 °F (low) to 64.9 °F (high). Annual precipitation averages 45.2 Inches. Annapolis is located in USDA Plant Hardiness Zone 6b. 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 | 21.4 °F | 37.6 °F | 3.11 in. |
| February | 24.3 °F | 42.6 °F | 2.45 in. |
| March | 33.2 °F | 53.4 °F | 3.47 in. |
| April | 43.6 °F | 65.9 °F | 5.11 in. |
| May | 54.2 °F | 75.7 °F | 4.82 in. |
| June | 62.9 °F | 84.3 °F | 4.89 in. |
| July | 65.6 °F | 87.5 °F | 4.37 in. |
| August | 63.4 °F | 86.5 °F | 3.03 in. |
| September | 55.7 °F | 81.0 °F | 3.4 in. |
| October | 44.2 °F | 68.6 °F | 3.7 in. |
| November | 34.1 °F | 54.0 °F | 3.78 in. |
| December | 26.0 °F | 42.0 °F | 3.07 in. |
| Annual | 44.1 °F | 64.9 °F | 45.2 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 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |