A summer storm rumbled across the Inland Empire, causing hundreds of lightning strikes, dropping marble-sized hail and flooding the 10 Freeway during rush hour, officials said Wednesday evening.
Flooding on the eastbound 10 Freeway near Cherry Avenue in Fontana forced lane closures and caused a six-mile backup, state transportation officials said. By 6:30 p.m., all lanes were open and traffic was moving.
In the last 24 hours, nearly 500 lightning strikes were reported in western Riverside County, according to the National Weather Service. Lightning strikes on Wednesday ignited two palm tree fires in Mira Loma, where hail the size of marbles covered the ground in some areas.
The agency said that more than 100 lightning strikes had been reported in the same period in southwest San Bernardino County.
The storm was caused by a volatile combination of low pressure off the California coast and monsoonal moisture over the region, according to the National Weather Service.
"When they combine, this is the type of scenario you get," said meteorologist James Thomas of the Weather Service office in San Diego.
Rainfall varied from 1/4 of an inch to more than 3/4 of an inch in some areas.
Murrieta recorded 0.45 inches of rain and 0.82 fell southwest of Beaumont in Riverside County. Wildomar near Lake Elsinore reported 0.73 inches, according to the Weather Service.
"It just rained for most of the day," Thomas said.
The storm activity was moving north on Wednesday evening. But forecasters said that the unstable weather could continue into Thursday.