Most county fairs in southwest Oklahoma take place in September, like the Oklahoma State Fair. County fairs across southwest Oklahoma hold many similar memories for residents. Most county fairs in southwest Oklahoma have already announced fair dates for 2026. All county fairs in southwest Oklahoma are typically hosted by each county's OSU Extension Office. READ MORE: Why Frederick, Oklahoma Feels Like Stars Hollow In FallThe Oklahoma State Fair will take place Sept. 17-27 in Oklahoma City.