The National Weather Service’s highest level red flag warning remained in effect in parts of Los Angeles and Ventura as dangerously strong winds—which could worsen the wildfires burning across the region—are expected to pick up overnight and peak on Wednesday morning as progress in containing the two largest blazes in the area remained slow.

Fanned by strong winds, the wildfires have killed at least 24 people and swept through 40,000 acres in the Greater Los Angeles area.

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