Understanding the Climate Conditions Behind the 2025 Los Angeles Urban Firestorm

Understanding the Climate Conditions Behind the 2025 Los Angeles Urban Firestorm

In January 2025, the Los Angeles foothill communities of Altadena and Pacific Palisades were consumed by an unprecedented urban firestorm, which ultimately destroyed over 16,000 structures and caused 31 fatalities. Understanding how climate dynamics contribute to large-scale fires is crucial for improving fire-weather forecasting and community preparedness.

In a recent publication, Southwest CASC-affiliated researchers examined the atmospheric conditions that gave way to the extreme surface winds fueling the Los Angeles firestorm. The researchers also looked into the dry fuel (grasses and other vegetation) that contributed to early fire ignition and growth. To understand the rarity of these conditions, researchers compared their findings to historic conditions during previous windstorms and other past destructive fires in California. 

Researchers found that the weather pattern behind the fire event was highly unusual. Strong, dry winds blew straight across the mountain ranges, forming intense downhill gusts outside of typical Santa Ana wind corridors. Although wintertime Santa Ana winds are common in this region, they rarely occur before the first winter rains. In this case, rain arrived later in the season, drying out plants and dead vegetation to dangerous levels. While there is no evidence that Santa Ana winds are becoming stronger or more frequent, the simultaneous occurrence of extreme winds and dry fuels is becoming an increasing fire risk factor, especially as temperatures warm and rainfall timing and amount become less predictable.

Many of the major destructive urban fires in recent years have shared the same broad wind patterns that characterized the 2025 Los Angeles firestorm. Although the National Weather Service accurately forecasted the “particularly dangerous situation” several days in advance, response systems were still overwhelmed. As communities continue to expand into fire-prone landscapes, this research emphasizes the importance of aligning improved forecasting with proactive planning and operational preparedness.

Read the full publication online at npj Natural Hazards.