The region could experience record-breaking temperatures through Sunday in some areas, especially in inland valleys, mountains, and deserts, where the risk of extreme heat is elevated. Temperatures are running 10 to 20 degrees warmer than normal for this time of year.

Excessive heat warnings for the valleys and deserts of San Diego County have been extended through Monday night, as a high-pressure system remains parked over California.

A heat advisory for the mountains has also been extended over the next few days.

The situation is very different along the immediate coast, where lifeguards have reported visibility of less than a mile since 1 p.m. this week due to dense fog.

The coastal marine layer will deepen on Thursday, keeping foggy conditions at the beach and possibly bringing difficult driving conditions farther inland, such as coastal mesas and higher terrain, during the morning commute.

A slight dip in temperatures is expected on Friday as the heat dome shifts slightly to the east, though it appears it will change course and return to California over the weekend.