The order will be in effect from sunrise to sunset, which marks the 22nd anniversary of the attacks.
A moment of silence is also scheduled for 8:46 a.m. nationwide.
Gov. Mike DeWine has ordered all U.S. and Ohio flags to be lowered Monday in honor of those killed on Sept. 11, 2001.
The flags should be flown half-staff upon all public buildings and grounds throughout the state, a statement by DeWine’s office said.