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?

A strong and dry Santa Ana event with extreme fire weather conditions is increasingly likely,” the NWS said in a statement. “This event may be considerably stronger for many areas than the event that we experienced this past Monday through Wednesday.

Wildfires fueled by strong Santa Ana winds have devastated Southern California, destroying thousands of homes and causing 27 deaths. The fires, affecting urban areas and the Olympic preparation, are worsened by climate change and urban expansion.