Ontario, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 15.1 °C (high). Annual precipitation averages 1067.3 Millimeters. Ontario is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.9 °C | 0.7 °C | 81.03 mm |
| February | -7.1 °C | 2.2 °C | 57.91 mm |
| March | -2.6 °C | 7.6 °C | 75.69 mm |
| April | 3.6 °C | 15.3 °C | 101.85 mm |
| May | 9.9 °C | 21.4 °C | 110.49 mm |
| June | 14.8 °C | 25.8 °C | 125.98 mm |
| July | 16.6 °C | 27.9 °C | 108.71 mm |
| August | 15.6 °C | 26.9 °C | 92.71 mm |
| September | 12.1 °C | 23.7 °C | 83.57 mm |
| October | 5.7 °C | 16.7 °C | 77.22 mm |
| November | 0.1 °C | 9.2 °C | 76.45 mm |
| December | -4.5 °C | 3.3 °C | 75.69 mm |
| Annual | 4.7 °C | 15.1 °C | 1067.3 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |