Rockdale, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.8 °F (low) to 60.2 °F (high). Annual precipitation averages 39.4 Inches. Rockdale 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 | 16.1 °F | 31.7 °F | 2.08 in. |
| February | 18.9 °F | 35.7 °F | 1.92 in. |
| March | 28.5 °F | 47.6 °F | 2.41 in. |
| April | 39.0 °F | 60.7 °F | 3.88 in. |
| May | 49.8 °F | 71.6 °F | 4.77 in. |
| June | 59.9 °F | 81.0 °F | 4.62 in. |
| July | 63.8 °F | 84.6 °F | 4.31 in. |
| August | 62.4 °F | 82.8 °F | 4.1 in. |
| September | 54.6 °F | 77.1 °F | 3.4 in. |
| October | 42.5 °F | 63.9 °F | 3.28 in. |
| November | 31.8 °F | 49.3 °F | 2.46 in. |
| December | 21.9 °F | 36.9 °F | 2.12 in. |
| Annual | 40.8 °F | 60.2 °F | 39.35 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 |