The event in Denver on Tuesday will include Gov. John Hickenlooper and emergency response officials.
The shootings at an Aurora theater on July 20 left 12 dead and 58 injured.
The Waldo Canyon and High Park fires this summer destroyed more than 600 homes and left three people dead.
The 9/11observance will mark the terrorist attacks on the World Trade Center, the Pentagon and a plane that crashed near Shanksville, Pa.
(Copyright 2012 by The Associated Press. All Rights Reserved.)