Essex, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.6 °F (low) to 60.6 °F (high). Annual precipitation averages 38.4 Inches. Essex is located in USDA Plant Hardiness Zone 5b. 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 | 16.0 °F | 31.8 °F | 2.1 in. |
| February | 19.0 °F | 36.0 °F | 1.85 in. |
| March | 28.5 °F | 48.1 °F | 2.41 in. |
| April | 38.8 °F | 61.1 °F | 3.69 in. |
| May | 50.3 °F | 72.2 °F | 4.63 in. |
| June | 60.2 °F | 81.6 °F | 4.61 in. |
| July | 63.7 °F | 84.5 °F | 4.21 in. |
| August | 61.8 °F | 82.8 °F | 3.81 in. |
| September | 53.7 °F | 77.6 °F | 3.29 in. |
| October | 42.0 °F | 64.4 °F | 3.15 in. |
| November | 31.5 °F | 49.5 °F | 2.55 in. |
| December | 21.7 °F | 37.0 °F | 2.09 in. |
| Annual | 40.6 °F | 60.6 °F | 38.39 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°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 |