Summer thunderstorms have arrived in the Southern California mountains and have the potential to affect Tuesday evening's commute. 

As a result, the KCAL News team has issued a Next Weather Alert to help you prepare for the possible storm heading for the San Gabriel Valley. 

The alert will remain in effect until at least 8 p.m. and potentially through 9 p.m., depending on how the conditions evolve. 

The National Weather Service has issued a special weather statement for Pomona, Glendora and Covina. The NWS expects wind gusts to reach 50 mph, and half-inch-sized hail could strike those cities Tuesday afternoon. 

NWS meteorlogists have also issued a flash flood warning for parts of the Inland Empire, including Riverside, San Bernardino, Fontana, Moreno Valley and Ontario. 

The heavy rain has already dropped 1 to 2 inches in the area. Meteorologists estimate rainfall rates of .25 inches to .75 inches per hour. An additional .5 to 1.5 inches of rain is possible.

The thunderstorms forced most beaches in Orange County to close.