Sudden Summer Monsoon Drenches High Desert Area

An hourlong “monsoon” rumbled across the High Desert on a scorching Friday afternoon, dumping more than an inch of rain in some spots and prompting flash-flood warnings through the mountains and passes.

Southern California’s midsummer version of Desert Storm struck hardest in Beaumont, in the shadow of the San Bernardino Mountains about 80 miles east of Los Angeles, where 1.29 inches of rain fell in less than an hour.

The temperature in Beaumont had reached 104 degrees just before the storm struck about 4:15 p.m. and then plunged into the 70s.

“It rained so hard down here it blew off our rain gauge,” said Capt. John Mijares of the California Department of Forestry from his station in Beaumont.

Mijares said there was no major damage reported, although some streets were flooded.

“We got everything all at once, winds of 20 to 30 m.p.h., rain so strong there was zero visibility and a whole host of traffic accidents out on I-10,” he said. “Cars were scattering everywhere, but fortunately no injuries.”

Constantine Pashos, meteorologist with the National Weather Service in Los Angeles, said the storm developed after moist air from Arizona circulated at a high altitude above the San Bernardino Mountains.

Extremely hot air moving upward from the ground caused the moisture to condense into rain clouds.

“Basically, what we have here is what we call the summer monsoon pattern,” Pashos said.

The storm was accompanied by thunder and lightning throughout the mountains.

“We had hundreds and hundreds of lightning strikes but no damage we know of yet,” Capt. Dan Petrinovich said from the forestry department’s Garner Valley Station above Idyllwild. “But we expect to have what we call ‘sleepers’ . . . trees and buildings that will flame up tomorrow (when) things dry out.”

The effects of the storm were felt in widely scattered areas of northwest Riverside County and southwest San Bernardino County.

But in Banning, four miles from Beaumont, there were almost no signs that a storm had occurred.

“Just a few sprinkles here,” a Banning police dispatcher said.