Hillsboro, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 41.7 °F (low) to 61.6 °F (high). Annual precipitation averages 38.1 Inches. Hillsboro 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 | 15.7 °F | 32.4 °F | 1.46 in. |
| February | 19.3 °F | 37.0 °F | 1.77 in. |
| March | 29.7 °F | 49.8 °F | 2.41 in. |
| April | 40.7 °F | 63.0 °F | 3.73 in. |
| May | 52.4 °F | 73.2 °F | 5.24 in. |
| June | 62.1 °F | 82.4 °F | 4.97 in. |
| July | 65.8 °F | 86.0 °F | 4.15 in. |
| August | 63.6 °F | 84.5 °F | 3.71 in. |
| September | 54.9 °F | 77.9 °F | 3.63 in. |
| October | 43.3 °F | 65.0 °F | 2.97 in. |
| November | 31.7 °F | 50.0 °F | 2.28 in. |
| December | 21.6 °F | 37.5 °F | 1.76 in. |
| Annual | 41.7 °F | 61.6 °F | 38.08 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |