Rain moving through SoCal could delay your holiday travel - What you need to know

LOS ANGELES (KABC) -- The second of two storm systems is bringing periods of heavy rain, significant flood risk and thunderstorms to Southern California, causing dangerous travel conditions as the holiday rush begins.

Thursday is expected to be one of the busiest days at the Los Angeles International Airport, and with the rain, travelers are urged to plan ahead. Several flight departures were delayed Thursday morning, most of which were within half an hour of their scheduled time, but that could change later in the day.

According to TSA, the busiest days of the holiday season (locally and nationally) are projected to be Thursday, Dec. 21 and Friday, Dec. 22 as well as Thursday, Dec. 28 and Friday, Dec. 29.

The best advice? Plan to arrive at the airport two to three hours ahead of your scheduled departure time.

"We suggest to pre-book your parking ahead of time," said Glenda Silva with Los Angeles World Airports. "We have now opened up a new lot called our LAX Budget, that's a location where you can park now for anywhere between $15 to $20 a day."

The storm, which will last until Friday, brought flooding to the Bay Area on Wednesday and is now dumping rain and gusty winds on Southern California. Santa Barbara and Ventura counties are in the bull's-eye for the heaviest rain and flooding on Thursday, with the National Weather Service issuing its second-highest flood threat forecast for the counties.

Oxnard in Ventura County recorded about one month's worth of rain in just 40 minutes on Thursday morning. Some people were rescued from their cars after they became trapped on flooded roads.

By Friday morning, the heavy rain and potential flooding will move into L.A. and cities to the south. The rain will also move into the Phoenix area on Friday. Flash flooding, hail and thunderstorms are possible.

ABC News contributed to this report.