With another scorching weekend in store for SoCal, fire danger is ticking up

Southern Californians are in for yet another scorching weekend.

The National Weather Service has issued a heat advisory for much of the region through Monday, with temperatures expected to hit their peak on Sunday.

Highs in the San Fernando Valley, San Gabriel Valley and other inland areas of L.A. County are expected to range from the mid-90s to about 105 degrees. Downtown Los Angeles and much of Orange, Ventura and Santa Barbara counties will get up to the lower 90s. Beaches will also be hot — in the lower 80s.

Moving farther east, things get really toasty. Forecasters have issued a more severe extreme heat warning for parts of the Inland Empire, where temperatures could get up to 108 degrees, and for the Coachella Valley, where they could hit 120.

Humidity will likely also continue to add to the discomfort, but will be concentrated in areas closer to the coast, where it will keep nighttime temperatures relatively warm and make it more difficult to cool down. Inland areas will feel drier.

Those who are most at-risk from the heat are people who work or spend time outside, people without access to air conditioning and those who are either over 65 or young children.

Forecasters are also warning of dangerous rip currents and swells along the coast this weekend.

If you’re headed to the beach to beat the heat, as many Southern Californians likely are, they recommend staying out of the water or, if you do go swimming, stay in front of lifeguards. It’s also a good idea to avoid jetties and tidal rocks.

Wildfire risk

This weekend will also come with a high risk of wildfires.

Forecasters warn that fire danger will be elevated through at least Monday, driven by heat, dry vegetation and low humidity levels away from the coast.

Despite some extra moisture in the air over the last several weeks, there hasn’t been enough to actually produce rain. Without precipitation, and under consistently high temperatures, plants will continue to dry out and become fuel.

“We have humidity, but it's not reaching the saturation point. Therefore, we won't have a cloud. We won't have precipitation,” said Rong Fu, an atmospheric scientist at UCLA who specializes in weather patterns and wildfires.

Fu said a system of high atmospheric pressure sitting over the Western U.S. is pushing warm, dry air across the Sierra Nevada from inland deserts and into Southern California.

That can generate what’s known as downslope wind. Those winds plus the already dry conditions align to create some especially dangerous fire weather.

One spark can easily turn into a large blaze, and humans are the most common cause of wildfires in Southern California, according to the U.S. Forest Service.

People can accidentally start wildfires in a range of ways, including throwing a lit cigarette into dry brush or dragging a chain behind a vehicle, creating sparks. One of the most common human causes is improperly extinguished camp fires.

Lightning can also start wildfires but is unlikely under current weather conditions. Southern California has seen minimal thunderstorms this summer.

The new normal?

Heatwaves in the summer and fall are obviously not new for Southern California, but they are getting worse.

Much of the heat currently blanketing the region is being driven by the high-pressure system, which traps warm air and compresses it against the ground, heating it even further. Forecasters say it’s likely to stay that way through the end of July.

But high-pressure systems like this one usually don’t stick around this long.

“For this pattern to linger almost two weeks — yeah, I would say, from a climatological point of view — that's pretty unusual,” Fu said.

One major driver of the change, Fu said, is climate change: As the climate warms, this kind of “anomalous” high pressure system will become stronger and more frequent.

And one consequence of hotter and longer heatwaves, is extended elevated periods of risky fire weather.