In California, more than 2 million of the state's 13.5 million homes sit in high to severe wildfire regions. To view the numbers of homes in low, moderate and extreme areas, scroll over each county for details. The criteria for determining wildfire risk in each county include: Fuels -- trees, grass and brush that feed fuels; slope -- the grade of the surrounding land that impacts the speed and intensity of a wildfire; access -- condition of roads leading to the area.