Much of California faces an early season heat wave this week as high pressure over the Southwest expands westward.

Significant heat is expected to be in full effect in Southern California on Tuesday, excluding some coastal areas, the National Weather Service said.Just in time for the summer-like blast of heat, many Los Angeles city pools reopened Monday, but smog and outdoor activities were a concern for air quality regulators who said an ozone advisory would be in effect through Saturday.

Red flag warnings for fire danger were set to be in effect Monday evening through Wednesday morning along the south Santa Barbara County coast due to gusty winds. Southern California Edison was considering shutting off power to nearly 5,200 customers in the county to prevent fires.

Critical fire weather conditions were also expected in southeastern California.

Temperatures will soar well into triple digits in the San Joaquin and Sacramento valleys by Thursday. Some areas could reach 113 degrees, forecasters said.

Interior valleys and mountains of the east and north San Francisco Bay region will also see rising temperatures but onshore flow near the coast should limit heat risks, the weather service said.

An excessive heat watch was in effect for the Long Beach area, among other areas, on Tuesday, when temperatures are expected to reach a high 89 degrees.