A flash flood warning has been issued for southeastern San Diego County until 6:30 p.m.
Radar estimated rainfall in excess of one inch in the last hour west of Pine Valley near Interstate 8.
Areas that may experience flooding include Cuyamaca Rancho State Park, I-8 between Pine Valley and Boulevard, southern Mount Laguna, Lake Morena, Highway S1 between Lake Cuyamaca and Mount Laguna, Pine Valley, Descanso, Campo and Lake Cuyamaca.
Residents in the East County were rattled by thunder and lightning as monsoon moisture moved across the region Thursday.
Dark clouds filled the skies over Pine Valley just before 2 p.m. and an NBC 7 news crew captured a strong thunder clap and lightning strike.
Coastal zones have a 20 percent chance of thunderstorms and so the National Weather Service has extended a beach hazard statement through 8 p.m. Lightning is also possible.
Higher than average waves of 5 feet, and powerful rip currents are also of concern. Beachgoers are encouraged to swim near a lifeguard.
While our coast and inland areas will begin to feel less humid starting Friday, our mountain and desert areas retain a chance of a thunderstorm through Monday of next week.