Southern California’s recent wildfires were driven by a combination of long dry spells, warm weather, and strong Santa Ana winds, according to UCLA climate and wildfire scientist Alex Hall in comments released on May 20. The region saw multiple fires this week, including the Sandy fire in Ventura County that has led to more than 40,000 evacuations and significant blazes in Riverside, San Diego, Santa Barbara counties, and the Channel Islands’ Santa Rosa Island.
The situation highlights how certain weather patterns can dramatically increase wildfire risk. Hall said that categorizing the severity of Santa Ana wind events similarly to hurricanes could help agencies and communities better prepare for dangerous conditions. “Southern California experienced a Santa Ana wind event this week following a very dry spring and unusually warm conditions. Our research shows that when dry vegetation coincides with strong Santa Ana winds, wildfire risk becomes very high. Under those conditions, if an ignition occurs, there is a strong likelihood that a large fire will develop,” Hall said.
He further explained: “Most catastrophic Southern California fires begin as preventable ignitions during extreme but identifiable conditions.” Hall noted the role of human activity: “While the weather and vegetation conditions were highly favorable for wildfire spread, the fire still required an ignition source. In Southern California, most ignitions are accidentally or purposely human-caused.” He added: “These fires are usually not inevitable natural events. Without human-caused ignitions, many of these fires would not occur, even during periods of elevated fire weather.”
Hall advocated for new approaches to classifying these wind events: “Our research suggests that combinations of strong Santa Ana winds, prolonged dryness and unusually warm conditions create recognizable high-risk windows for catastrophic fire.” He continued: “Southern California will ultimately benefit from a more standardized way of characterizing extreme Santa Ana fire weather… analogous to hurricane categories.” According to Hall: “I would consider the recent Santa Ana winds a ‘Category 4 or 5’ event,” noting not all such events pose equal danger depending on moisture levels.
Hall directs both UCLA’s Sustainable LA Grand Challenge and Institute of the Environment and Sustainability; his team found Los Angeles-area fuels were about 25% drier due to climate change when major January 2025 wildfires began. The University of California Los Angeles operates within the University of California system on its 419-acre campus supporting academic excellence across scholarship, arts and athletics while fostering diverse perspectives through its programs; it has been associated with Nobel laureates and MacArthur Fellows according to the official website.
Looking ahead, researchers believe improved classification systems could support public communication efforts as well as emergency response planning during future high-risk periods.
