Roberts, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.9 °F (low) to 61.5 °F (high). Annual precipitation averages 37.9 Inches. Roberts is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.7 °F | 32.9 °F | 2.2 in. |
| February | 19.6 °F | 37.4 °F | 1.83 in. |
| March | 29.1 °F | 49.0 °F | 2.57 in. |
| April | 39.6 °F | 62.5 °F | 3.75 in. |
| May | 51.5 °F | 73.5 °F | 4.39 in. |
| June | 60.8 °F | 82.1 °F | 4.44 in. |
| July | 63.6 °F | 84.6 °F | 4.12 in. |
| August | 61.2 °F | 83.1 °F | 3.55 in. |
| September | 53.3 °F | 78.7 °F | 2.99 in. |
| October | 41.9 °F | 65.9 °F | 3.29 in. |
| November | 31.5 °F | 50.5 °F | 2.69 in. |
| December | 21.8 °F | 37.6 °F | 2.08 in. |
| Annual | 40.9 °F | 61.5 °F | 37.9 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 |