As fire crews battle major blazes in the Los Angeles area, Northern California remains largely free of wildfire risk thanks to a stark contrast in weather patterns.

High pressure is building from the north and that will help to tighten the pressure gradient over southern California, producing more gusty winds.

Southern California — with sprawling cities, clogged freeways and heavy industry — is already notorious for some of the worst air quality in the nation. This week's wildfires are putting millions of people at risk for immediate health problems and longer term issues.