Volkswacht Bodensee - Wildfires around Los Angeles blanket city in smoke

Three separate blazes have erupted around the United States' second biggest city, fueled by a punishing heat wave and fanned by gusting winds.

Thousands of firefighters, with support from the US National Guard, were battling to slow the spread of fires tearing through tinder-dry brush.

There have been no reports of deaths or serious injuries, but tens of thousands of homes and businesses are being threatened by the looming flames.

The fast-moving Airport Fire in Orange County has consumed more than 9,000 acres (3,600 hectares) since it was started accidentally on Monday afternoon by workers operating heavy equipment.

The blaze, to the southwest of Los Angeles, was spewing thick smoke into the air, sparking the closure of nearby schools.

Orange County Fire Authority Captain Steve Concialdi said the fire was continuing to grow and bearing down on Santiago Peak, home to radio and television broadcast towers used by local media outlets as well as federal and local government agencies.

Concialdi said crews had been working to protect the peak but had to withdraw from the area because the flames got too intense.

Airplanes could be seen dumping red retardant on hillsides above a well-to-do neighborhood, as helicopters dropped water on the flames.

To the northeast of Los Angeles, the Line Fire has now consumed nearly 28,000 acres (11,300 hectares) in San Bernardino County.

Resort communities popular with tourists around Lake Arrowhead and Big Bear were being told to evacuate, and a number of major access roads were blocked.

Firefighters were battling the blaze from the air as ground crews sought to establish containment lines, trying to create breaks in the vegetation to prevent the fire from spreading further.

But gusting winds and hot, dry weather was making conditions difficult.

Cal Fire, which is coordinating the fight against the blaze, said the north and east sides of the fire continued to move agressively, with challenging conditions expected throughout the day.

"Tuesday night, stronger winds are predicted which could lead to drops in relative humidity and greater fire spread," the agency said.

The smaller Bridge Fire to the north of Los Angeles began Sunday and had destroyed more than 4,000 acres (1,600 hectares) by Tuesday afternoon.

A persistent heat wave that has gripped much of southern California for a week continued to make conditions difficult.

Officials said the excessive heat -- with temperatures as high as 110 Fahrenheit (43 Celsius) -- along with gusting winds would create "potential for large vertical plume growth and visible smoke columns."

Forecasters said Tuesday was likely to be the last day of extreme temperatures in the region, with a rapid cooldown expected from Thursday.

Wildfires are a natural part of the wilderness cycle and are not unusual in California and other parts of the US West at this time of year.

After two relatively mild fire years, 2024 is shaping up to be significant.

Two very wet winters generated abundant growth of vegetation, which has now dried out after a long, hot summer, leaving behind lots of fuel.

M.Betschart--VB