Awlaki, who was an American citizen, was killed by a drone strike in Yemen on Friday. The fact that he was American is what makes the situation unique, the State Department said in its advisory issued on Saturday.
"Awlaki's standing as a preeminent English-language advocate of violence could potentially trigger anti-American acts worldwide to avenge his death," the advisory read.
The drone strike that killed Awlaki was authorized by a secret Department of Justice memorandum, The Washington Post reported.
U.S. Citizens are encouraged to enroll in the Smart Traveler Enrollment Program, which makes it easier for embassies and consulates to get in touch in the event of an emergency.
The State Department's advisory expires on Nov. 30.