Forecasters expect Wednesday will be noticeably windier than Tuesday and firefighters warned that vegetation is critically dry.

Here's a guide to understanding "particularly dangerous situation" red flag warnings, containment, and other terms related to the devastating fires that have left much of the LA area in ruins.

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.

Much of southwest California is under a red flag warning, with winds expected to peak Wednesday. Authorities are urging residents to heed evacuation orders and prepare for power outages.