Millions of Southern Californian residents have been advised to limit outdoor activities due to poor air quality caused by ongoing wildfires, according to the US National Weather Service (NWS).

The NWS has issued several air quality alerts covering the South Coast Air Basin, Coachella Valley, and eastern Riverside County.

Strong Santa Ana winds and extreme fire weather are forecast for portions of Los Angeles and Ventura counties starting Monday. These winds are expected to strengthen overnight, particularly in the wind-prone areas of Los Angeles and Ventura counties, according to NWS Los Angeles.

The South Coast Air Quality Management District has issued a windblown dust and ash advisory, which will remain in effect through Tuesday evening due to strong winds throughout the region.

The NWS has also issued Red Flag Warnings, High Wind Warnings, and Wind Advisories for much of the area.

Last week, local authorities confirmed that fierce wildfires across Southern California had claimed the lives of at least 27 people and destroyed more than 12,300 structures after over a week of devastation.

The Palisades Fire, the largest active wildfire in the Los Angeles region, has burned 23,713 acres (95.96 square km). The fire, which began on January 7, is 31 percent contained, an increase from 22 percent earlier in the week.

“Overnight and this morning, cooler temperatures, light winds, and good humidity were observed,” said the California Department of Forestry and Fire Protection (Cal Fire) in an update on Friday. “Crews continue to establish and improve containment lines to minimize fire spread around structures within controlled areas and ensure public and incident personnel safety.”

Another major fire, the Eaton Fire, was 65 percent contained as of Friday morning, up from 55 percent the previous day. The fire has burned 14,117 acres (57.1 square km) near Altadena and Pasadena.

Cal Fire stated that firefighters continue to work on improving containment lines in steep, hard-to-reach areas. The fire’s containment continues to grow, and it is expected to remain within its current footprint.

Local officials announced that as many as 11,000 residents would be allowed to return to their neighborhoods after some evacuation orders were lifted on Thursday. However, residents must show proof of residency to access these areas, while some other zones devastated by the wildfires will remain closed to the public.