Wildfires and ‘a Category 4 or 5 Santa Ana event’

Southern California's long dry spell and warm weather meant the region was primed for the current wildfires when strong Santa Ana winds hit this week - similar to the winds and conditions that sparked Los Angeles County's devastating Palisades and Eaton fires in January 2025, said UCLA climate and wildfire scientist Alex Hall.

The 1,700-acre Sandy fire has already led to more than 40,000 evacuees in Ventura County's Simi Valley, about 40 miles from downtown Los Angeles. Riverside County faces the 1,500-acre Bain fire and 500-acre Verona fire, while a massive 17,000-acre blaze consumes national parkland on the Channel Islands' Santa Rosa Island. Farther afield are the 800-acre Tusil fire in San Diego and 500-acre Foothill fire in Santa Barbara County.

Categorizing the severity of Santa Ana winds in a similar way as hurricanes could help preparation in the future, Hall said.

Causes:

• "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."
• "Most catastrophic Southern California fires begin as preventable ignitions during extreme but identifiable conditions."
• "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."
• "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."

Taking Santa Anas as seriously as hurricanes:

• "Our research suggests that combinations of strong Santa Ana winds, prolonged dryness and unusually warm conditions create recognizable high-risk windows for catastrophic fire."
• "Southern California will ultimately benefit from a more standardized way of characterizing extreme Santa Ana fire weather, analogous to hurricane categories, to help agencies and communities better prepare for the highest-risk conditions."
• "The idea isn't to classify the fire itself, but rather the underlying Santa Ana fire-weather conditions that can give rise to catastrophic fires if an ignition occurs. Analogous to hurricane categories, a Santa Ana severity framework could combine factors like wind intensity, humidity, prior dryness/lack of rainfall and unusually warm conditions that further dry vegetation."
• "I would consider the recent Santa Ana winds a 'Category 4 or 5' event."
• "Not all Santa Ana events are equally dangerous from a wildfire perspective. Some occur under relatively moist conditions and produce little fire activity, while others occur after prolonged drying and create extreme risk conditions. Our research suggests that catastrophic Southern California fires tend to occur during identifiable combinations of atmospheric and fuel conditions. A standardized severity framework could potentially help improve public communication, preparedness, utility coordination, ignition prevention efforts and emergency response during the highest-risk periods."

Feel free to quote from Hall's comments to add climate context to your wildfire coverage. Alex Hall is a climate scientist, professor and director of both the Sustainable LA Grand Challenge and Institute of the Environment and Sustainability. Through UCLA's Climate & Wildfire Research Initiative, Hall and others found that LA fire fuels were 25% drier due to climate change when the January 2025 Palisades and Eaton fires began.