Hillsdale, 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 °F (high). Annual precipitation averages 38.5 Inches. Hillsdale 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 | 14.2 °F | 30.2 °F | 1.61 in. |
| February | 17.8 °F | 34.7 °F | 1.79 in. |
| March | 28.5 °F | 47.6 °F | 2.51 in. |
| April | 39.6 °F | 61.1 °F | 3.74 in. |
| May | 51.4 °F | 72.4 °F | 4.81 in. |
| June | 61.4 °F | 81.6 °F | 4.91 in. |
| July | 65.0 °F | 84.7 °F | 4.25 in. |
| August | 62.8 °F | 82.8 °F | 4.08 in. |
| September | 54.5 °F | 76.7 °F | 3.58 in. |
| October | 42.7 °F | 63.9 °F | 2.9 in. |
| November | 30.9 °F | 48.6 °F | 2.32 in. |
| December | 20.5 °F | 35.7 °F | 2.03 in. |
| Annual | 40.8 °F | 60 °F | 38.53 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 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 |