Southern California’s extreme heat might finally come to an end

Brace yourselves, Southern Californians. A break from the heat is on its way.

You just might have to wait another day, according to the National Weather Service.

In its Tuesday morning forecast, the weather service says “a significant cooling trend will begin today as onshore flow returns,” but cautions that “temperatures will still be in the 90s to lower 100s across the mountains and warmer valleys.” Excessive heat warnings will remain in place for Los Angeles and Ventura counties.

In the L.A. basin, most places are expected to cool by as much as 10 degrees Tuesday. Inland areas will still hover in the 80s and 90s, while temperatures could dip into the 70s along the coast.

By Wednesday, it’s expected to cool another 10 degrees before temperatures settle at a level a little below average on Thursday, with highs in the 70s and 80s, according to National Weather Service meteorologist Robbie Munroe.

Humidity throughout the week is expected to be 10% to 20%, but it’s expected to be less dry by Thursday, as the marine layer deepens and carries moisture to the area.

Orange and San Bernardino counties are expected to have similar conditions, with the Inland Empire being the warmest and driest area in the region.

The weather service issued a red flag warning, signaling dangerous conditions for fire growth, for the mountains around Angeles National Forest, including the area of the Bridge fire, until noon Wednesday.

Red flag conditions are also expected to continue in the San Gabriel Mountains and expand into the Interstate 5 corridor and Antelope Valley through early Wednesday.

Over the last several days, the heat has combined with gusty winds to create conditions ripe for extreme fire growth. Fires have broken out in Los Angeles, San Bernardino and Orange counties that have filled the air with smoke and ash, creating a hazard for residents.

On Tuesday, the South Coast Air Quality Management District issued an air quality alert that was in effect through the night because of increased fine particle pollution from wildfire smoke in Orange County and the Inland Empire.

Winds are estimated to be 20 mph or stronger across the region’s hillsides Tuesday, driving flames and pushing smoke into nearby communities.

“It’ll literally fan the flames,” said Philip Gonsalves, a meteorologist with the National Weather Service in San Diego. “It increases the rate at which the fire will spread. That’s the bad news. The silver lining is that the direction of spread becomes a little more predictable.”

An air quality alert due to increased fine particle pollution from the wildfire smoke is in effect until 11 p.m. Tuesday across Orange County inland areas and the Inland Empire.

Corona-Norco Unified School District announced that Wilson Elementary, Temescal Valley Elementary and Todd Elementary were closed Tuesday along with their after-school programs because of poor air quality. The district, which consists of about 50 schools, also canceled outdoor activities and athletics at all schools until further notice.