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.

Nearly 100,000 San Diegans could loose power during the next round of power shutoffs after the National Weather Service issued another Red Flag Warning for the region for Monday and Tuesday as Santa Ana winds return.

NWS' 3:40 a.m. advisory indicates winds were blowing northeast at speeds between 25 to 35 mph, with gusts up to 60 mph.