Lying in the humid continental zone, Ohio has a generally temperate climate. Winters are cold and summers mild in the eastern highlands. The southern region has the warmest temperatures and longest growing season—198 days on the average, compared with 150 to 178 days in the remainder of the state. More than half of the annual rainfall occurs during the growing season, from May to October.

Among the major cities, Columbus, in the central region, has an annual mean temperature of 51°F (11°C), with a normal maximum of 61°F (16°C) and a normal minimum of 42°F (6°C). Cleveland, in the north, has an annual mean of 50°F (10°C), with a normal maximum of 59°F (15°C) and minimum of 41°F (5°C). The mean temperature in Cincinnati, in the south, is 53°F (12°C), the normal maximum 63°F (17°C), and the normal minimum 43°F (6°C). Cleveland has an average of 127 days per year in which the temperature drops to 32° (0°C) or lower, Columbus 124 days, and Cincinnati 99 days. The record low temperature for the state is –39°F (–39°C), set at Milligan on 10 February 1899. The record high is 113°F (45°C), registered near Gallipolis on 21 July 1934.

Cleveland has an average annual snowfall of 56.3 in (143 cm), while Columbus receives 28 in (71 cm), and Cincinnati 24 in (61 cm). Cincinnati had the most average annual precipitation (1971–2000), with 42.6 in (108 cm), compared with 38.5 in (97.8 cm) for Columbus and 38.7 in (98.3 cm) for Cleveland. Because of its proximity to Lake Erie, Cleveland is the windiest city, with winds that average 11 mph (18 km/hr).