Thunder and lightning brought heavy rain to the Antelope Valley and parts of the San Gabriel Mountains late Sunday night.
The National Weather Service is calling for a hot and humid day Monday, with another chance of thunderstorms for some desert and mountain locations during the morning hours.
Anyone who hears thunder is warned to seek shelter indoors or in a hard top vehicle.
The unusual weather pattern prompted a red flag warning to be issued for Santa Barbara and San Luis Obispo counties, as well as the Ventura County mountains until 10 a.m.
Officials are concerned about lightning strikes and hot temperatures bringing an increased risk of fire danger.
Residents are asked to report any smoke or wildfires immediately.
Afternoon temperatures are expected to be warm, but remain near the average for this time of year in most areas through the week.