Another Day on Griddle Is Forecast : Weather: After cooling it during an unusually mild summer, San Diegans swelter in a sizzling autumn heat wave.

After a cool, overcast summer, hot weather struck San Diego County with a vengeance Thursday with the temperature at Lindbergh Field shooting up to 92 degrees, matching a record for the date set 20 years ago, forecasters said.

Another hot day is expected today, with temperatures gradually cooling over the weekend.

Official temperatures around the county reflected the Santa Ana condition: 11 of the 26 weather stations reporting posted temperatures above 100, while eight posted temperatures in the 90s.

County residents responded by setting a new record for electric demand, according to San Diego Gas & Electric Co.

As residents cranked up air conditioners, 3,057 megawatts of electricity were used, breaking the old record of 3,047 megawatts set Sept. 11, 1990.

Despite the record heat, air quality actually improved over Wednesday, the Air Pollution Control District reported.

A health advisory warning against vigorous outdoor activity was issued for an area extending from the coast 20 miles inland after smog levels reached 175 on the pollution standard index in Kearny Mesa on Wednesday. Air quality above 100 is considered unhealthful.

On Thursday, Kearny Mesa recorded a 92 on the index, but the warm air inversion layer that traps pollution close to the ground could return, said a spokesman for the district.

Thursday got off to a hot start with a temperature of 85 at Lindbergh Field by midmorning, forecaster Wilbur Shigehara said.

By 2 p.m., the temperature had slid back down to 82, with a cooling sea breeze blowing, but, by 4:15 p.m. the mercury had shot back up to 92, Shigehara said. A temperature of 102 was posted in Alpine; 82 at Cabrillo National Monument; 94 at Campo; 94 at Chula Vista; 91 in Coronado; 84 in Del Mar; 106 in El Cajon; 108 in El Centro; 105 in Escondido, 109 in Fallbrook, 90 in Imperial Beach; 102 in La Mesa; 75 at the Oceanside Harbor; 107 in Poway; 106 in Santee and 103 in Vista.

“This is the second heat wave we’ve had since fall arrived,” Shigehara said. “Is this an Indian summer or what?”

The first fall heat wave hit last week with three days in the 80s, Shigehara said.

The temperature Thursday was an abrupt contrast to the 77-degree high Wednesday and the normal high of 75 degrees, he said.

For the second time this month, two school districts in East County were forced to close non-air-conditioned schools shortly after noon Thursday and may close them early again today, officials said.

Grossmont Union High School District closed four of its 10 schools and Cajon Valley Union closed six of its 24 schools, officials said.

La Mesa-Spring Valley will close all 21 of its elementary schools an hour early today, the superintendent’s office said.

As the Santa Ana weakens, temperatures are expected to come down 5 to 8 degrees today, but it will still be hot, Shigehara said.

Temperatures at the beaches will range from 70 to 78 today and 68 to 74 over the weekend, he said. The surf is rolling in at 2 to 4 feet, and the ocean temperature is 67 degrees.

In the coastal areas and inland valleys, a high today of 77 to 85 is expected, 72 to 80 over the weekend. Nighttime lows will drop to 62 to 67, Shigehara said.

Inland areas will heat up to 92 to 102 today, cooling to 87 to 97 on Saturday and 80 to 90 on Sunday, he said. Nights will dip to 55 to 63.

In the mountains, temperatures are expected to hold steady at 75 to 80 today and through the weekend, with nighttime lows of 55 to 65.

The mercury in the desert is due to reach 105 to 110 today, falling slightly to 103 to 108 over the weekend. Nights will range from 65 to 75.