Flat Rock, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.9 °C (low) to 15.5 °C (high). Annual precipitation averages 1025.1 Millimeters. Flat Rock is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.6 °C | 0.8 °C | 68.07 mm |
| February | -6.8 °C | 2.3 °C | 55.88 mm |
| March | -2.3 °C | 7.8 °C | 71.12 mm |
| April | 3.4 °C | 15.3 °C | 100.58 mm |
| May | 9.8 °C | 21.6 °C | 103.38 mm |
| June | 15.2 °C | 26.6 °C | 108.46 mm |
| July | 17 °C | 28.7 °C | 106.93 mm |
| August | 15.9 °C | 27.7 °C | 90.68 mm |
| September | 11.9 °C | 24.4 °C | 95 mm |
| October | 5.8 °C | 17.5 °C | 77.72 mm |
| November | 0.5 °C | 9.8 °C | 72.64 mm |
| December | -4.2 °C | 3.6 °C | 74.68 mm |
| Annual | 4.9 °C | 15.5 °C | 1025.14 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 |