The storm brought heavy rain to large swaths of the Southland, triggering severe flooding on local roads. L.A.'s Union Station was inundated, making a mess for travelers.
Magic Mountain, which was also closed the previous day due to inclement weather, announced the Thursday closure on Twitter.
Knott's Berry Farm also announced its closure on social media, adding that its California Marketplace dining and shopping area will remain open until 7 p.m.
The region's two other major theme parks, Universal Studios Hollywood and Disneyland, remained open.
PARK UPDATE: Due to inclement weather, #SixFlagsMagicMountain will be CLOSED today, December 30.— Six Flags Magic Mountain (@SFMagicMountain) December 30, 2021