Orange County environmental health officials warned local swimmers this week to avoid contact with ocean water, especially in spots close to storm drains, creeks and rivers.

A rain advisory is in effect for the entire Orange County coast, including Newport Beach, Laguna Beach and Huntington Beach, after runoff from this week's storm caused elevated bacteria levels.

The advisory, which is intended to reach recreational ocean, bay and harbor users, went into effect after more than two-tenths of an inch of rain fell, Orange County Health Care Agency Water Quality Supervisor Mike Fennessy said.

He said the heightened bacteria levels can last for about three days after a heavy rain. Urban runoff, he said, which typically comes from fertilizers, road oils, litter, animal waste and decomposing vegetation, makes for risky swimming conditions.

Those who choose not to heed such recommendations, Fennessy said, could suffer sinus and upper-respiratory infections or gastrointestinal problems.

"Those are the big three," he said.

While officials encourage swimmers to stay out of the water when rain advisories are in effect, Fennessy said, typically beach closures are reserved for "sewage spill events."

Human sewage, he said, is more likely to cause illness than other types of runoff.

According to the National Weather Service's website, sun is expected for Friday in Orange County, and slight chances of rain are in the forecast for Saturday and Sunday .

For more information about the rain advisory, visit the county's water quality website at ocbeachinfo.com.

jill.cowan@latimes.com

Twitter: @jillcowan