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 NWS has reissued a 'particularly dangerous situation' warning for swaths of Los Angeles and Ventura counties, cautioning of high wind gusts, dry air and a higher risk of rapid fire spread and extreme fire behavior.

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.

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

As firefighters struggle to gain control of massive and deadly wildfires that are raging across parts of the Los Angeles area, the region is once again bracing for the potential of new fires and for current ones to intensify as a new storm system heads for the state.

The National Weather Service has issued a Red Flag waning for a wide swath of Southern California as Santa Ana winds are expected to bring dangerous fire weather to the region later this week.