Wednesday, December 24, 2025

Heavy Rain, Flooding, Mudslides Could Make Holiday Travel Dangerous in Altadena, Pasadena

Officials are warning Pasadena and Altadena residents to prepare for hazardous driving conditions today as a powerful atmospheric river storm is expected to cause widespread flooding, mudslides and debris flows across the region on Wednesday and Thursday. 

The National Weather Service said rainfall rates ranging from 0.6 to 1.25 inches per hour, with localized downpours up to 1.5 inches on south-facing mountain slopes, will make roads treacherous.

“There will almost certainly be numerous rockslides and mudslides along with areas of severe flooding in urban locations and along freeways, which is why being out on the roads will be exceptionally dangerous,” NWS meteorologist Ariel Cohen said at a Tuesday news conference. 

He urged travelers to reconsider plans that call for driving on Christmas Eve and Christmas Day. 

Lower elevations such as downtown Pasadena are expected to receive 2 to 4 inches of rain, while other areas could see 4 to 8 inches. That includes foothill terrain above Pasadena and Altadena, where saturated soil and canyon roadways increase the risk of slides. 

A flood watch went into effect at 4 p.m. Tuesday and remains in place through Thursday evening for much of Los Angeles County, covering foothill and mountain areas near recent burn scars. 

Evacuation warnings and orders have been issued for neighborhoods near the Eaton Fire. 

Periods of heavy rain are expected to continue through Christmas Day, with sporadic showers Friday and Saturday. Snow levels are forecast to drop to around 7,000 feet later in the week, but forecasters said snow will not be a major factor in this storm.