The National Weather Service issued a heat advisory covering Manhattan Beach, Hermosa Beach, Redondo Beach, El Segundo and Hawthorne, with temperatures of 85 to 105 degrees expected.

The advisory takes effect Wednesday, Sept. 9, at 10 a.m. and runs through Thursday, Sept. 10, at 8 p.m. Temperatures are forecast to run 10 to 15 degrees above normal, with heat peaking Wednesday. The NWS said the advisory could be extended into Friday, according to the Whittier Daily News.

The advisory specifically covers Los Angeles County Beaches and the Palos Verdes Peninsula, zones that include all five South Bay cities.

Dangerous heat will start building Tuesday, Sept. 8, before the advisory officially begins. Downtown Los Angeles and Long Beach could see highs of 96 to 98 degrees, with inland and valley communities topping 105, the Los Angeles Times reported. Overnight lows Tuesday and Wednesday night are expected to stay in the 70s, offering little of the usual nighttime cooling.

Relief won't come at night.

The heat follows a weekend of coastal flooding, rain and high surf from the remnants of Tropical Storm Marie. David Gomberg, lead meteorologist at the NWS in Los Angeles-Oxnard, told the Los Angeles Times that lingering moisture from the storm will compound the problem.

"If the clouds don't materialize, then Wednesday could be a real problem, and temperatures could really jump up," Gomberg said.

He also reminded residents to drink plenty of fluids, stay in air-conditioned rooms and check up on vulnerable relatives and neighbors.

South Bay beachgoers face a compound hazard. The Los Angeles County Department of Public Health issued an ocean water quality advisory for all LA County beaches until at least 2 p.m. Wednesday, Sept. 9, cautioning swimmers to avoid water contact for at least 72 hours after rainfall, NBC Los Angeles reported. A high surf advisory and coastal flood advisory were also in effect through 11 p.m. Tuesday, Sept. 8.

The NWS advises residents to drink three to four cups of water every hour when exposed to heat, take breaks in cool or shaded areas, limit alcohol and caffeine, and stop activity if experiencing nausea, dizziness or unusual fatigue.

Los Angeles County operates cooling centers during excessive heat events. Residents can find locations and hours through the county's cooling center locator.