The continuing rain has left Southern California beaches polluted by urban runoff, and the water should be avoided for at least 72 hours once the rain ends, health officials warned this week.

A rain advisory for Los Angeles County beaches was in effect through at least 6 p.m. Thursday, meaning beachgoers should avoid contact with ocean water, according to the county Department of Public Health.

Rain advisories were also in place for beaches in Orange County, where the Health Care Agency reported ocean water bacteria levels exceeding state health standards, and in Ventura County.

Elevated bacteria levels from rainstorms can cause illness, especially in the children and elderly, the L.A. County Department of Public Health warned.

Areas of the beach not near discharging storm drains, creeks, and rivers are safe to visit, the department stated.

More than 70 outfalls from L.A. County’s 2,800-mile storm drain system disperse trash, pet feces, pesticides, automotive fluids, and human gastrointestinal viruses into the ocean, according to Heal the Bay, a Santa Monica-based environmental advocacy group.

Nearly 1 million cigarette butts per month are dropped on county streets, and many wash into the ocean, according to the group, which advocates reforming the county’s stormwater system.