‘Historic Weather Forecast’: As Fires Rage, Santa Ana Winds Expected to Become Damaging Overnight

Santa Ana winds are expected to flare up Wednesday night and Thursday morning, giving firefighters across Southern California a further test as multiple large fires continue to blaze.

The region’s week of extremely critical fire weather may reach its peak during this time period.

Wind gusts of 60 to 80 mph are likely across mountains in Los Angeles and Ventura counties, with gusts of up to 60 mph in valleys, causing extreme fire danger, the National Weather Service said.

Smoke and flames rise from the Creek Fire on Dec. 6, 2017. (Credit: KTLA)

Smoke and flames rise from the Creek Fire on Dec. 6, 2017. (Credit: KTLA)

"Extremely critical conditions now appear likely across parts of Ventura and Los Angeles counties late tonight into early Thursday morning. These dangerous high-end critical to extremely critical conditions will continue into .... Thursday," a weather service outlook read.

Related: Latest details on Southern California wildfires

Thursday is also expected to see an extremely low relative humidity of 4 percent, Los Angeles Fire Department Chief Ralph Terrazas said at a news conference on the Creek Fire.

The agency’s measurement of the threat of wildfire – its “brush burning index” – is at 296 for Thursday, the chief said.

“This is the highest number I’ve ever seen in my career,” said Terrazas, who joined the department in 1983.

Firefighters appear tiny next to flames from the Creek Fire on Dec. 6, 2017. (Credit: KTLA)

Firefighters appear tiny next to flames from the Creek Fire on Dec. 6, 2017. (Credit: KTLA)

Meant to give firefighters a sense of the “threat level,” the index is in the extreme range when it’s above 165, Terrazas said.

Gusts of 65 to 75 mph are expected in a “significant wind event” overnight Wednesday into Thursday, the chief said.

Cal Fire Incident Commander Ron Bravo called it a "historic weather forecast."

"This is a challenging time for all of us," Bravo said.

The weather service has issued a high wind warning from 10 p.m. Wednesday to 4 p.m. Friday, with damaging wind gusts of 60 to 80 mph. A red flag warning for extremely critical fire weather is in effect through 8 p.m. Saturday.

Fire and police officials repeatedly warned anyone near fires to be ready to evacuate, with cars packed with crucial items.