This article reprinted from The conversation under a Creative Commons license.
Dry conditions across Southern California in early January 2025 set the stage for a series of deadly wind-driven fires that burned thousands of homes and other structures in the Los Angeles area.
Ming Pan, a hydrologist at the University of California-San Diego’s Center for Western Weather and Water Extremes, tracks the state’s water. Put Southern California’s drought into perspective using charts and maps.
How Dry Is Southern California Right Now?
In early January, soil moisture in much of Southern California was less than 2 percent of the state’s historical records for that day. That is very low.
Hydrologists in California watch the skies very closely starting in October, when California’s water year begins.
The province receives very little rain from May to September, so autumn and winter are important to fill the lakes and build a snowpack to provide water. California relies on the Sierra snowpack for about one-third of its fresh water.
However, Southern California started the 2024-25 water year extremely dry. The region received some rainfall in the atmospheric river in November, but not much. After that, most of the tropical cyclones that hit the West Coast from October to January turned north over Washington, Oregon, and Northern California.
When the air is warm and dry, wind and evaporation also absorb water from plants and soil. That leaves dry vegetation that can provide flying coal fuel to spread wildfires, as the Los Angeles area saw in early January.
