The declaration allows state emergency personnel to help local communities with storm-related cleanup.
The cleanup of the mess left behind by this week's storm will take a while.
On Monday, crews will begin work in the burn areas. They're set to clear sediment from the Mullally Debris Basin in La Canada Flintridge.
In February, the Mullally basin overflowed, sending mud and rocks into the neighborhood below. Dozens of homes were destroyed.
Since the disaster, the basin was expanded, and officials said it worked as designed.
This time around, there was no overflow and no homes were damaged.
But steep slopes mean the area is always at risk of slides.