Region’s weather logs 40 degrees of separation

Where it was hot and steamy in Southern California on Wednesday afternoon, it was really hot and steamy.

And where it was relatively cool and comfortable, it was pretty darn cool and comfortable for late August.

All told, Wednesday’s weather yielded an unusually wide temperature divide, a gap of more than 40 degrees between oceanfront and desert. The region’s heat was enough to set or tie records in San Gabriel and at a couple of spots in the Coachella Valley, where the mercury rose well into the triple digits. That kind of heat, or a very close facsimile, is expected to persist through the Labor Day weekend.

The pattern was expected to continue today with high temperatures from the 70s at the beaches to the 90s inland, said Bill Hoffer, a spokesman for the National Weather Service. He said relative humidity would probably increase to 60%, with some isolated showers and thunderstorms.

Statewide, the demand Wednesday for air-conditioning strained California’s power grid, prompting a Stage 1 electrical emergency calling for residential and commercial users to conserve.

But at Malibu’s Zuma Beach, the day’s high temperature was a relatively chilly 69 degrees.

“It was kind of an average day. We didn’t even reach 70,” said Brent Katzer, a lifeguard captain. His advice to folks sweltering in inland and mountain areas: “Come down to the beach and enjoy the cool weather!”

Stuart Seto, a specialist at the National Weather Service, agreed. At least through the Labor Day weekend, he said, “The places to go are either the beaches or the malls.”

“Once you get inland, there’s not much of a break” in the heat forecast for the next several days, he said. And the slight temperature declines that might come in Southern California’s hot zones probably will be offset, in some cases, by rising humidity.

The culprit behind the high temperatures is a heat-sealing high-pressure system centered in Arizona but extending well into Southern California. It is producing a shallow marine layer, which means that less of the region is enjoying cooling ocean breezes.

At the same time, ocean waters are cooling, generating ample natural air-conditioning for the low-altitude zones along the beaches.

So, in Newport Beach, the day’s high climbed only to 73 degrees, a full 10 degrees below the record for Aug. 29. LAX posted a high of 74 degrees, a far cry from that location’s record 90 degrees.

“It’s absolutely gorgeous. Sunny and windy and beautiful,” crowed Steve Nelson, manager of a Laguna Beach pizzeria. The closest thing he offered to a weather complaint was that conditions were “a little humid.”

But seemingly a world away in the Coachella Valley town of Thermal, a visitor would have encountered a high of 117 degrees, tying a record set in 1984. Indio came in at a record-tying 116.

And although only a few areas endured record highs, there was plenty of heat to go around. Los Angeles County’s hottest spots were Woodland Hills and Newhall, both hitting 109. San Gabriel hit 107, a record high.

Jesse Narvaez, 39, a construction worker who is taking courses to switch to a nursing career, stopped by Woodland Hills’ Pierce College shortly before 3 p.m., less than an hour after temperatures were peaking, to take care of some paperwork. He was cheerful, but sweating heavily, as he returned to his car.

“My back right now is completely soaked just from walking from one side of campus to the other,” Narvaez said.

To save gas, he planned to drive with the windows down and without using the air conditioner. But at his commercial construction job Wednesday, Narvaez said, he felt “blessed to be working indoors. We have the AC at full blast.”

Throughout California, the cranking up of air conditioners contributed to the Stage 1 alert, which lasted from 3:20 p.m. until 5:30 p.m. Demand peaked at 48,538 megawatts -- the highest usage for the year, but not a record.

The California Independent System Operator, which manages the flow of electricity across most of the state, said it expected Thursday’s demand to be about 49,600 megawatts, still below the record of 50,270 megawatts set during July 2006. Another Stage 1 emergency is likely, and that could worsen to a Stage 2 emergency if power supplies can’t keep up with demand, said Gregg Fishman, a Cal-ISO spokesman.

The agency declares a Stage 1 emergency when electricity reserves fall below 7%; the designation triggers a call for voluntary power usage cutbacks.

Under a Stage 2 emergency, reserves have fallen below 5%, and the grid operators begin to curtail power to commercial and other customers who have volunteered to accept cuts when needed.

On Wednesday, the power grid “held up really well,” Fishman said. But he warned that demand would keep growing and electricity supplies would be stretched tighter this summer because the intensifying drought had hurt hydroelectric power production.

The bottom line, Fishman said, is that “we need to have everything going well when we hit these kinds of peak demand periods.”

stuart.silverstein@latimes.com

elizabeth.douglass@latimes .com

Nardine Saad, an editorial assistant in Orange County, contributed to this report.