The vegetation was parched, and the air was dry. The worst windstorm in a decade had arrived.

All it would take was a spark.

As a fire ignited in the Pacific Palisades on Tuesday, the winds crashed over and through the mountains like white water rapids. Winds as strong as those in a hurricane propelled the flames through dense urban neighborhoods, and swirling fire whirls danced from home to home, leaving a trail of destruction in their wake.

Since November, the extremely dry vegetation has been blasted by regular Santa Ana winds, sparking first the Franklin fire in November, then the Malibu fire in December, and now this week’s blazes, which are thought to be the most destructive Los Angeles has ever seen. Ahead of each cycle, the National Weather Service has issued a warning for a “particularly dangerous situation,” a newer kind of higher-level alert that was intended to be used only every two to three years.

The current cycle of Santa Ana winds began on Tuesday with the first of four wind events that are expected to continue into next week and likely beyond, fostering fire activity and hampering firefighting efforts.

The second event began Friday morning, and it was expected to diminish by Friday afternoon. It was slightly weaker than the first, but it still brought winds of 80 to 90 miles per hour to the mountains of Southern California.