Rain from a powerful winter storm that swept across Southern California has begun to taper off, but another storm system was on the horizon for Christmas Day with showers and possible thunderstorms.

Forecasters said Southern California could see its wettest Christmas in years and warned of flash flooding and mudslides. Areas scorched by wildfires in January saw evacuation warnings as heavy rains and gusty winds brought mudslides and debris flows.

Many flood areas were in burn scar zones, which were stripped of vegetation by fire and are less able to absorb water.

San Bernardino County firefighters said they rescued people trapped in cars Wednesday when mud and debris rushed down a road leading into Wrightwood, a resort town in the San Gabriel Mountains about 80 miles (130 kilometers) northeast of Los Angeles. It was not immediately clear how many were rescued.

Firefighters also went door-to-door to check homes, and the area was under a shelter-in-place order, officials said. An evacuation order was issued for Lytle Creek, also in the San Gabriel Mountains.