Wednesday, December 24, 2025

Arriving ‘Pineapple Express’ Storm Won’t Reach Peak Intensity Until Midmorning Wednesday

[National Weather Service]

National Weather Service labels system “very dangerous” with flood watch in effect through Thursday

The atmospheric river storm forecast to bring dangerous flooding and debris flows to Los Angeles County had not yet reached peak intensity in Pasadena and Altadena as of early Wednesday, with the most hazardous period expected to extend through midday as heavier rainfall moves into the region.

As of 3:15 a.m. Wednesday, light rain had begun across the area, but “the heaviest rainfall has not yet arrived,” according to an early-morning status summary compiled from official forecasts and public safety reports.

“We’ll be closely monitoring all day,” Pasadena Chief Communications Officer Lisa Derderian said early Wednesday.

A Flood Watch was in effect for Pasadena, Altadena and much of Los Angeles County from Tuesday afternoon through 10 p.m. Thursday, and a Wind Advisory remained in effect for the Pasadena-Altadena area into Thursday afternoon.

County officials said evacuation warnings tied to the Eaton Fire burn scar began Tuesday morning, with sheriff’s deputies and local police departments tasked with notifying affected residents.

Mandatory evacuation orders were in effect for 124 homes in unincorporated Los Angeles County areas, according to the Los Angeles County Sheriff’s Department, while broader evacuation warnings covered larger portions of Altadena and parts of Pasadena and Sierra Madre near the Eaton Fire burn scar.

Los Angeles County Sheriff Robert Luna said deputies notified residents door-to-door in areas under mandatory evacuation orders and urged residents not to delay leaving until conditions worsen. He warned that waiting could put lives at risk as rainfall intensifies.

In Pasadena, Derderian said city officials did a “door knock on approximately 10 homes that are under evacuation warning.”

Forecast: Heavy rain rates, debris-flow risk

Forecasters warned rainfall rates could reach 0.6 to 1.25 inches per hour across many areas, with localized downpours up to 1.5 inches per hour possible on south-facing mountain slopes.

In the Pasadena-Altadena foothills, areas impacted by the Eaton Fire were assessed at Phase 2 risk for debris and mudflows, indicating a moderate threat during the forecast period.

Projected storm totals included 5 inches to more than 7 inches of rain in Altadena through Thursday and 4 to 6 inches in Pasadena during the same period, according to the early-morning status report.

The National Weather Service described the system as a “very dangerous” storm, warning of significant urban flooding, rapidly rising creeks, debris flows and the potential need for swift-water rescues.

Early reports: No major damage yet in Pasadena or Altadena

As of early Wednesday morning, there were no official reports of home damage, debris flows or mudslides in Pasadena or Altadena overnight.

Fire officials have warned that burned hillsides stripped of vegetation can no longer absorb rainfall effectively, allowing runoff to move quickly downhill and pick up ash, rocks and debris, significantly increasing the risk of fast-moving debris flows during intense storms.