With Santa Ana winds developing slowly and weaker than originally anticipated, the National Weather Service has delayed implementation of "particularly dangerous situation" red flag warnings -- which were supposed to begin early Tuesday morning -- until 3 a.

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.