The NWS Weather Prediction Center has issued a rare High Risk (level 4/4) for excessive rainfall across Southern California from Wednesday, December 24, through the morning of Thursday, December 25, 2025.
- The potential for high hourly rainfall totals will intensify runoff over soils that are relatively dry or within recent burn-scar areas, greatly increasing the risk of flash flooding.
- This environment is expected to produce landslides, rock falls, and mudslides across vulnerable terrain.
- The greater-than-normal travel anticipated during the Christmas holiday will likely expose a larger number of people to these life-threatening hazards, a factor taken into consideration by forecasters when upgrading the event to a High Risk.
A strong atmospheric river is forecast to impact Southern California beginning late Tuesday and continuing through Thursday morning, December 25.
As a result, the U.S. National Weather Service (NWS) Weather Prediction Center (WPC) has issued a High Risk (level 4/4) of excessive rainfall, the highest category used in the agency’s outlooks and reserved for events with a high probability of widespread, life-threatening flash flooding.
According to the WPC Excessive Rainfall Discussion issued early Tuesday, a stream of moisture-laden air associated with an amplifying Pacific trough will bring sustained onshore flow and strong vertical ascent across Southern California…