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.

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.

The National Weather Service on Wednesday extended the wildfire warning through the end of the week for much of East County.