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

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.

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,