Cooler temperatures and potential rain is coming to southern California this weekend, but with increased fire risk in a region where the state’s largest blaze this year is already burning.

The National Weather Service is predicting scattered showers and thunderstorms in the southern half of the state on Saturday, along with some cooler temperatures over the weekend that could finally bring some temporary relief to a prolonged heat wave scorching the region.

National Weather Service meteorologist John Dumas said despite potential wet weather and lower temperatures, fire risk may only increase.

In a pattern referred to as virga, the moisture in the middle layers of the atmosphere will fall as rain, but evaporate before hitting the ground, Dumas said.

“Unfortunately, the lightning can still make it,” Dumas said, which might spark new wildfires.

That could worsen conditions for fire personnel working around the clock to extinguish the Lake fire in Santa Barbara County, California’s largest so far this year. That blaze has grown to 37,742 acres, but firefighters have worked to contain the blaze around the Santa Ynez and Los Olivos region where structures were threatened.

Crew members have made a “visible difference” on the south side of the fire in recent days, where flames could previously be seen from Santa Ynez and the Lake Cachuma area, said Capt. Scott Safechuck, spokesperson for the Santa Barbara County Fire Department

Firefighters have worked through nights to make some progress on the blaze with controlled burns of dry vegetation and a water-dropping helicopter. Those coordinated efforts have “really been successful for us eliminating a lot of the threat on the south side,” Safechuck said.

Risk of fire-igniting dry lightning have led to weather officials issuing a red flag warning until 9 pm Saturday for the mountain and foothill regions of Los Angeles County, according to the weather service, along with the Antelope Valley and valleys of San Luis Obispo and Santa Barbara Counties, Ojai and Casitas Valley.

Dumas said weather service officials have tools that can both track in real time and model likely lightning strikes, which helps firefighters on the ground.

Dumas also said the heat will decrease by one or two degrees over the next few days, leading to “almost normal temperatures” by Monday or Tuesday before a new heat wave is expected to roll through Southern California.