Labor Day storm pounds Palm Springs area; North Indian Canyon reopens

Mother Nature provided an early wakeup call to many Coachella Valley residents Monday as a series of overnight thunderstorms brought almost an inch of rain and sustained lightning and thunder to the desert.

The mesoscale convective system – or a complex of organized thunderstorms – moved into Southern California from Arizona just after 1 a.m. and pounded the area for several hours with strong winds, blinding rain and a vivid lightning show.

The storms left flooded streets, numerous power outages, the largest single-day rainfall in Palm Springs in more than six months and probably a few sleepy individuals who had to work on the Labor Day holiday.

By 5 a.m. Monday, the National Weather Service said the storms delivered 137 cloud-to-ground and 6,319 in-cloud lightning strikes in west Riverside County alone.

Most of the lightning across southern California occurred in Riverside County, with just 3 cloud-to-ground strikes recorded across southwest San Bernardino, San Diego and Orange counties.

By the time the storms moved out, more than 2,070 Southern California Edison customers were without power in Palm Springs and Whitewater, but officials could not determine if those were all a result of the storm. 

A much larger Southern California Edison power outage of 10,775 customers affected Desert Hot Springs later Monday afternoon. The power company's website attributed the outage to storm conditions.

The National Weather Service issued a flash flood watch for more possible storms, which was in effect until 8 p.m. Labor Day. Small chances of thunderstorms are possible for Tuesday and Wednesday as well.

While storms did not affect the desert floor during the day Monday, new storms formed over the Santa Rosa and San Jacinto mountains that prompted a severe thunderstorm warning and a flash flood warning.

Palm Springs police closed N. Indian Canyon Drive at the wash Monday morning because of flooding. It was the only known road closure in Palm Springs and it reopened just after 9:30 a.m. Tuesday.

Just under an inch – 0.98 inch – of rainfall was reported at the Palm Springs airport.

The heavy rain equaled the wettest day in Palm Springs since the Valentine's Day storm dumped 3.69 inches. In fact, Palm Springs collected more rain early Monday than had fallen over the last six and one-half months combined.

"I think the worst is over for now," meteorologist Miguel Miller said, although he cautioned more rain could come Monday afternoon.

In Thermal, 0.39 inch was recorded, and 0.27 inch in Desert Hot Springs, the weather service said. As of 7:30 a.m., the Palm Springs Aerial Tramway had recorded 2.24 inches of rain at its Mountain Station atop Mt. San Jacinto, according to  its website.

The storms could be traced to weather conditions in Arizona that pushed moisture and humidity westward into Southern California. Although Miller considered Monday's weather "freaky," it's not unusual for late August or early September.

"It happening this time of year is right on schedule," Miller said.

In Riverside County, Caltrans said US-95 was closed at Wind River Road in Blythe due to flooding. There was no estimated time for reopening. 

In San Bernardino County, State Route 62 was closed at Parker Dam Road due to flooding, but had reopened by 5:15 a.m. Monday, Caltrans reported on Twitter.

"Rainfall rates today could exceed flash flood thresholds, particularly in the mountains and deserts," the weather service said. "This is most likely from late morning through early evening."

The service advised drivers to exercise caution, noting that runoff caused by very intense but brief rainfall can gather in arroyos and small streams as well as urban roadways. There was a risk of mudslides and debris flows in steep terrain and in burn areas, the service said.