Ohio spans USDA hardiness zones 5b to 7a, with most of the state falling into zones 6a and 6b. The coldest part of Ohio is zone 5b, located in a small area in Knox County. Zone 6a covers much of northern and central Ohio, including cities like Mount Vernon and Toledo. Zone 6b includes many of Ohio’s major cities such as Columbus, Cincinnati, Dayton, Akron, and Cleveland’s southern areas. The warmest zone, 7a, is found in the southernmost parts of the state and some areas near Cleveland

. To summarize:

• Zone 5b: Coldest, small area in Knox County (average minimum temperatures -15°F to -10°F)
• Zone 6a: Northern and central Ohio (average minimum temperatures -10°F to -5°F)
• Zone 6b: Southern and lower parts of Ohio including major cities (average minimum temperatures -5°F to 0°F)
• Zone 7a: Southernmost Ohio and some areas near Cleveland (average minimum temperatures 0°F to 5°F)

This range influences what plants can survive Ohio winters and guides gardeners on planting schedules and plant choices.