Millions of people across Southern California are under a Red Flag warning as a dangerous windstorm starting Tuesday could bring widespread destruction and extreme fire risk to the area, with emergency services braced to provide a huge response.

High pressure is building from the north and that will help to tighten the pressure gradient over southern California, producing more gusty winds.

The strongest winds likely reached their peak overnight in Southern California, but powerful offshore gusts will continue throughout the day on Wednesday as the winds start to blow more from the east to northeast.