LOS ANGELES (AP) — Californians were urged to ease off the air conditioning to conserve electricity, and schools in inland areas closed early Tuesday as the state sweltered through another day of triple-digit heat.

Operators of the state electricity grid declared a Flex Alert, calling on people to set their thermostats at 78 or higher and to avoid using major appliances until evening.

"Conservation is critical" because peak electrical demand will be a relatively large 47,500 megawatts, said a statement from the California Independent System Operator.

In San Bernardino, where a high temperature of 101 was forecast, students were to be released early from Arrowhead Elementary School and Cajon High School because of inadequate air conditioning. The school board building also was to close early.

At midafternoon, with temperatures ranging from the 90s to triple digits, Los Angeles firefighters responded to reports of heat problems among members of a group of about 40 teens hiking on Mount Lee — where the Hollywood sign is located. Fire Department spokesman Brian Humphrey said about 13 needed attention. KCAL-TV reported from a helicopter overhead that a pumper truck crew hosed down the group to cool them off.

California's power grid must handle high demand without help from the twin-reactor San Onofre Nuclear Generating Station, which has been offline since January following the discovery of damaged tubes in its steam generators.

The National Weather Service said temperatures would remain above normal from Santa Barbara County through southeastern California and in much of the San Joaquin Valley. Temperatures were expected to top 100 degrees in deserts and inland areas as they have for more than a week, although the highs were expected to be 2 or 3 degrees cooler than on Monday.

Highs were expected to hit the high 80s in the Los Angeles area and the high 90s in foothill communities such as Pasadena.

The weather also was humid and there was a slight chance of afternoon and evening thunderstorms in the mountains and deserts, according to a weather service statement.

Temperatures could dip over the next few days as a hot air mass over the state cooled slightly, but the weather will warm again toward the end of the week, the weather service said.

The air will be drier and that will at least end the threat of thunderstorms, the weather service said.

Lightning strikes from weekend storms set a number of fires in wilderness areas that scorched more than 1,000 acres and continued to burn.