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.

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.

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.

Cal Fire crews are responding to the scene of a brush fire in Ramona that broke out early Tuesday morning, threatening at least one structure.

By Jorge Garcia and Lisa Richwine LOS ANGELES (Reuters) -Red Flag warnings advising of extreme wildfire danger expired across the Los Angeles area late on Wednesday, but forecasters warned that dry and windy conditions will persist on Thursday,