Devastating fires in the Los Angeles region are driven by Santa Ana winds blowing from California and Nevada’s interior deserts to the Pacific Ocean.

The winds are common in California in the colder months, but they can sometimes help spread dangerous wildfires.

The Santa Ana winds occur when there is high pressure to the east, in the Great Basin, and a low-pressure system off the coast. Air masses move from high pressure to low pressure, and the more extreme the difference in the pressure, the faster the winds blow. Topography also plays a role.