In a routine test, 11 sirens for the Lake Casitas flood-warning system will wail at noon Wednesday between downtown Ventura and Casitas Springs, the area most vulnerable to flooding after a major earthquake.
The short siren test will be followed for 10 minutes by messages over a public address system in English and Spanish.
The sirens were installed to warn people to flee to higher ground if the dam holding back the lake should collapse after a quake.
Last year, the siren malfunctioned during testing. But in a later test officials worked out the kinks.