From www.cooperativeresearch.org

September 10, 2001: President Arrives at Longboat Key Resort; Tight Overnight Security Includes Surface-to-Air Missiles
At 6:30 p.m., President Bush arrives at the Colony Beach and Tennis Resort on Longboat Key, Florida. [Sammon, 2002, pp. 13; Sarasota Herald-Tribune, 9/10/2002] He is in Florida as part of a weeklong effort to place a national spotlight on education and reading, and visited a school in Jacksonville earlier in the day. [ABC News, 9/10/2001; Florida Times-Union (Jacksonville), 9/10/2001] In preparation for the president’s visit to the resort, all guests have been cleared out of the building “to make way for the invasion of White House staffers, aides, communications technicians—even an antiterrorism unit.” Overnight, snipers and surface-to-air missiles are located on the roof of the Colony and adjacent structures, to protect the president. “The Coast Guard and the Longboat Key Police Department manned boats that patrolled the surf in front of the resort all night. Security trucks with enough men and arms to stop a small army parked right on the beach. An Airborne Warning and Control System (AWACS) plane circled high overhead in the clear night sky.” [Sammon, 2002, pp. 13 and 25; Sarasota Herald-Tribune, 9/10/2002] Whether this is a typical level of security for a presidential visit, or is increased due to recent terror warnings, is unstated.

Is there evidence that "surface-to-air missiles" are always put on the roof of where the President stays or was this a rarity?