While skies were overcast and temperature cooler in East County Tuesday morning, officials warned that a wildfire that has scorched more than 17,000 acres and destroyed nearly a dozen homes and 25 other structures is not letting up and is expected to flare up again tonight.

“I want to be very clear in my message,” said Cal Fire San Diego Chief Tony Mecham at a news conference at Viejas Casino and Resort. “We have a sleeping giant in the backcountry.”

The National Weather Service has issued a red flag fire weather warning for most of San Diego County through 8 p.m. Wednesday.

Santa Ana winds blowing up to 50 miles an hour were expected to hit around 8 p.m. — pushing the fire from east to the west — and Mecham and other officials warned residents to be prepared.