A monsoonal storm ripped through the area Saturday afternoon, quickly cooling temperatures that had topped 110 degrees throughout Southwest County.

As the mercury inched up early in the day, air conditioners began to hum in homes throughout the region -- for a while anyway.

The heavy electrical use and the windswept rainstorm that left some downed power lines throughout the county prompted scattered power outages, leaving many people with few options to stay cool.

Officials with Southern California Edison said that, during the peak demand of the day, customers across parts of 11 counties used nearly 22,000 megawatts of electricity Saturday -- an all-time high for a Saturday. The day's peak usage matched last summer's high, which was recorded on a Tuesday, said Gil Alexander, an SCE spokesman.

Power was out for an unknown number of Menifee homes for at least four hours starting about 2 p.m. Brief outages were also reported in Murrieta, and some Temecula residents experienced intermittent power surges.

SCE officials could not provide a specific reason for the power outages, nor how many of the utility's customers were affected.

But they did speculate that the heat and the storm had something to do with it.

At 4 p.m., it was a sweltering 108 in Menifee -- and then the storm hit.

The downpour was accompanied by high winds, with some gusts reaching 41 mph. Signs and debris were tossed about and in the Ralphs parking lot at Antelope and Newport roads, shopping carts were swept away in all directions.

About half an inch of rain was dropped on the area during the deluge, causing some flooding on side streets and in area parking lots.

"It's a short period of heavy rain in a localized area," said Philip Gonsalves, a meteorologist with the National Weather Service.

The good news for residents who were passing time at home without an air conditioner was that the rainfall was accompanied by a 20-degree drop in the temperature.

"What happens is when it rains, it brings all the cooler air from the top of the atmosphere down," Gonsalves said. "Temperatures can drop 10 to 20 degrees."

In Temecula, residents contended with 110-degree heat until the storm hit just after 5:30 p.m. The high for the city was 111, which Gonsalves says is the hottest day Temecula residents have seen in at least a decade.

"It's the hottest I can remember," he said.

Power wavered repeatedly in the city between 4 and 6:30 p.m. John Tucker, who lives in Temecula, said the electricity at his home flickered nine times between 4 and 5 p.m.

Gonsalves described Saturday's weather as "pretty unusual."

"For one thing, most of the time when we have a monsoon, the storm stays over the mountain or the eastern slopes -- on the desert side," he said, referring to various mountain ranges that stretch from the Mexican border north into San Bernardino.

But not Saturday. The storms moved west, "which brings a temperature and humidity profile that we're not accustomed to west of the mountains," Gonsalves added.

While humidity levels in Southwest County are typically low -- in the 20 percent range --- they topped 55 percent throughout the area Saturday.

Gonsalves predicted that thunderstorms would linger into today.

"But I don't think we'll see as much activity in the valleys," he said.

Meteorologist Brandt Maxwell, also with the National Weather Service, predicted that temperatures for Southwest County would reach 106 degrees today, before easing up a tad to 98 Monday.

Staff writer David Carlson contributed to this report. Contact staff writer Brian Eckhouse at (951) 676-4315, Ext. 2626, or beckhouse@californian.com. To comment on this article, go to www.californian.com.