The most destructive wildfires in Los Angeles history Thursday have burned more than 54 square miles of land, destroyed thousands of structures and killed at least five people.

The red-flag warning extended Wednesday for the county’s inland valleys still is set to expire at 6 p.m. Friday, with overnight northeast winds of 28 to 38 mph and possible gusts of 50 mph, up to 60 mph after midnight.

Red flag criteria is generally when relative humidity is at 15% or less, combined with sustained winds and/or gusts of 25 mph or greater. Both of these conditions must occur simultaneously for at least 3 hours in a 12 hour period, according to the NWS.

That’s leading to the creation of mountain waves, which arise when strong winds blow perpendicular to a mountain range. The waves shoot down the coastal side of the mountains, gaining speed along the way, and are more casually referred to as simple Santa Ana winds.

The alert status for heightened combustion hazards in the county's inland valleys and mountains went into effect at 4 a.m. Wednesday and will last until 6 p.m. Friday.

San Diego County, which is in the midst of one of the driest periods on record, will be lashed by unusually cold and expansive Santa Ana winds early Wednesday that could spark wildfires, snap

The National Weather Service has issued a Red Flag Warning for San Diego County due to high winds and low humidity.

San Diego Gas & Electric began public safety power shutoffs Tuesday as San Diego County braces for a Santa Ana wind event and Red Flag Warning.

Tamara Berg shows where the red flag warning is in effect in the Los Angeles area. This forecast is from Jan. 9 at 6:30 a.m.

Amid an already dry winter season, the first Santa Ana wind event of 2025 is elevating fire danger this week and threatening power shut-offs for thousands of San Diego Gas & Electric customers.