Those heading to the beach this week are advised to stay out of the water as all Los Angeles County beaches are under advisory for excessive contamination from rainfall.

The advisory is in effect starting Friday and will remain until Monday, March 13 at 10 a.m. and could be extended depending on further rain activity, officials said.

The public is advised to stay out of the water due to heightened levels of “bacteria, chemicals, debris, trash, and other public health hazards from city streets and mountain areas likely to contaminate ocean waters at and around discharging storm drains, creeks, and rivers,” said the L.A. County Department of Public Health.

People who enter the ocean water during this period could become ill, officials warned. Those especially at risk include people with weakened immune systems, children and the elderly.

Rainfall arrived in the L.A. area on Thursday night, with periods of moderate to heavy rain expected to continue through Saturday, according to the National Weather Service.

Health officials recommend beachgoers avoid contact with ocean water for at least three days after significant rainfall.

Read the latest updates and beach advisories from the L.A. County Department of Public Health on its website.

Recorded information on current conditions is available through the county’s beach closure hotline at 1-800-525-5662.