The fires in Los Angeles county have been highly publicized lately and we've seen the videos of the flames raging. Geographical aspects and weather conditions such as the Santa Ana winds and dryness of the land itself, since California still is coming off of being in drought cause fires to spread rapidly.
https://earthobservatory.nasa.gov/blogs/earthmatters/2017/12/07/why-are-the-socal-fires-so-intense/
https://earthobservatory.nasa.gov/blogs/earthmatters/2017/12/07/why-are-the-socal-fires-so-intense/