The National Weather Service issued severe thunderstorm and flash flooding warnings for parts of central Los Angeles County, including Palmdale. The severe thunderstorm warning is in effect until 5:15 p.m., while the flash flood warning remains until 7 p.m.
The freak storm dropped rain, hail and even snow, NBC L.A. reports. Glendora residents living near the Colby Fire burn area were also urged to move their cars off the streets in case of flooding.
According to the NWS, the thunderstorm is capable of producing quarter-size hail and damaging winds over 60 miles per hour. They also noted that a tornado could develop, though it wasn't immediately likely.
The NWS has recommended anyone in the path of the storm seek shelter, preferably in a strong building away from windows.
"Prepare immediately for damaging winds, destructive hail, and deadly cloud to ground lightning," the NWS said in its alert.
The NWS also warned in its flash flood warning that most flash flood deaths occur when people are in their cars.
"Never drive your vehicle into areas where the water covers the roadway," the NWS said. "Flood waters are usually deeper than they appear. Just one foot of flowing water is powerful enough to sweep vehicles off the road. When encountering flooded roads, make the smart choice: Turn around. Don't drown."
This story has been updated.