A warning sign for contaminated beach water via San Diego County.

A rise in bacteria in San Diego’s beaches caused by urban runoff from this weekend’s storm prompted the Department of Environmental Health to issue an advisory Sunday.

Swimmers, surfers and other beach goers were warned that levels of bacteria can rise significantly in ocean and bay waters, especially near storm drains, creeks, rivers and lagoons that discharge urban runoff.

“Urban runoff may contain large amounts of bacteria from a variety of sources such as animal waste, soil and decomposing vegetation,” DEH spokesman Keith Waara said. “While many coastal storm drains within San Diego County are permanently posted with white metal warning signs, additional temporary warning signs are not posted for General Advisories.”

Activities such as swimming, surfing and diving should be avoided in all coastal waters for 72 hours following rain. This includes all coastal beaches and all of Mission Bay and San Diego Bay, according to DEH.

Elevated bacteria levels can persist after a rainstorm depending on the intensity of the storm, volume of runoff and ocean and current conditions.

— City News Service