The Santa Ana winds fanning wildfires that have killed at least 25 people in Southern California and destroyed more than 10,000 houses, businesses and other structures in Greater Los Angeles are flaring up again.

In recent days, however, the region’s powerful Santa Ana winds—which have been fanning the flames—have begun to slow down. This lull has offered firefighters a reprieve and a key opportunity to make progress against the blazes, but forecasts suggest the Santa Ana will return next week. What are these gusts, and how have they become so strong?

As the L.A. fires rage, we’re reminded of movies, books and songs that speak to the city’s love-hate relationship with the forces that shape it.

The winds fueling Southern California wildfires form when a high-pressure system develops over the Great Basin in Utah and Nevada

Santa Ana winds occur when air flows west from a region of high pressure over the dry Great Basin to lower pressure off the California coast, According to Accuweather. As that cool interior air flows over and through mountain passes, it accelerates, sinks and compresses.

Forecasters expect strong Santa Ana winds to return to the Los Angeles area this week with gusts up to 70 miles an hour in some places, putting firefighters in a race against time to control massive blazes that have killed 24 people and destroyed more than 12,