La Jolla's coast faces mid-80s temperatures under an extreme heat warning that runs through 8 p.m. Wednesday, Sept. 9.

The National Weather Service warning covers San Diego's coast, inland valleys and deserts, where temperatures are running 10 to 15 degrees above the typical upper-70s for early September. Once the warning expires, a heat advisory takes effect through Thursday evening, according to NBC San Diego.

The heat has already shattered records. Four Southern California cities set new highs on Monday, Sept. 7, according to the National Weather Service as reported by Fox 5 San Diego: San Diego reached 95 degrees, Vista hit 102, Oceanside Harbor reached 93 and Newport Beach hit 87.

NWS San Diego noted on Monday, Sept. 7 that the last time San Diego reached 95 degrees or higher two days in a row was almost six years ago, from Sept. 30 through Oct. 1, 2020.

Overnight lows are offering little relief. Temperatures will only drop to the lower-to-mid 70s for much of the county until the heat advisory ends at 8 p.m. Thursday, according to Fox 5.

Excessively high humidity is compounding the discomfort. The NWS attributed the moisture to a mix of monsoonal conditions and warmer-than-usual ocean temperatures. Post-Tropical Cyclone Marie is adding to the humidity across the county.

The heat prompted San Diego Unified School District to cancel all middle school athletics activities scheduled for Tuesday, Sept. 8. SDUSD Athletics confirmed the cancellation on X.

Beachgoers face compounding hazards. A coastal flood advisory and high surf advisory are in effect through 11 p.m. Tuesday, Sept. 8, for San Diego County coastal areas including La Jolla. The NWS forecast swells of 6 to 7 feet and warned of possible tidal overflow during evening high tides.

A predicted tide of 6.8 feet at La Jolla at 7:54 p.m. Tuesday marked the highest in a series of rising evening tides that began at 6.0 feet on Saturday, Sept. 5, according to NWS data reported by the Sacramento Bee.

Candace Hadley, public information officer for San Diego Fire-Rescue and Lifeguards, urged caution during a similar heat wave in late August. "Just be mindful of those conditions. Talk to the lifeguards, swim in front of a lifeguard tower, and watch your little ones," Hadley told Fox 5 on Aug. 25.

The NWS urged residents to drink plenty of fluids, stay in air-conditioned rooms and stay out of the sun. The agency warned that car interiors can reach lethal temperatures in minutes. Dozens of free Cool Zone locations across San Diego County are open for residents seeking relief.

Cooler temperatures and lower humidity are not expected to arrive before Sunday, Sept. 13.