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.

Red flag weather warning: A National Weather Service alert that warns the public — especially fire officials and firefighters — that strong winds are expected in specific areas of Southern California, and that there will be potentially dangerous fire weather conditions within the next 12 to 24 hours.

Dangerous fire weather conditions and poor air quality are expected to stick around until the weekend. Here's what to know in Orange County.