Ohio Gov. Mike DeWine has approved a plan to allow 30 percent capacity at home games for the Cincinnati Reds and Cleveland Indians to begin the 2021 season.

Great American Ballpark in Cincinnati (12,695 maximum capacity) and Progressive Field in Cleveland (10,512) will be allowed to host fans with detailed social distancing and mask-wearing policies in place under the ruling.

Still, the number of fans at stadiums across the United States varies widely.

Most teams are allowing fans at their spring training sites, but far below maximum capacity and with safety restrictions related to COVID-19 enforced.

No fans were permitted for regular-season games in 2020, a pandemic-shortened season capped with a neutral-site World Series in Texas. MLB allowed 11,000 fans for the NLCS and World Series at Globe Life Park in Arlington.

MLB and the state of Ohio have not revealed whether capacity could be increased later in the 2021 season as other markets continue to wrestle with proposals for fan admittance.

Chicago Cubs owner Tom Ricketts told CNBC last week that he's hopeful Wrigley Field and other stadiums will be close to capacity by the end of the season.

There is no ruling yet in Illinois as to whether the Cubs or Chicago White Sox will host fans for Opening Day.

In New York, Yankee Stadium was approved to host 5,500 fans and the Mets will be permitted to have around 4,500 at Citi Field when their home seasons open.

California, where coronavirus safety restrictions have been strict, has made no final decision about letting fans in Dodger Stadium for the World Series champions' home opener on April 9.

Angel Stadium is set to open April 1 with the Angels in action against the White Sox, but current restrictions make fan attendance uncertain.

There could be more immediate relief in sight for the Padres. San Diego County Supervisor Jim Desmond on Thursday requested Gov. Gavin Newsom allow fans to return to Petco Park.

"Many other cities and teams have changed the way they operate to keep their fans safe, by limiting areas where they can congregate and making masks mandatory," Desmond said in a letter to Newsom.