Halloween Threatened by Rain: Pineapple Express Could Complicate Southern California

• Tropical moisture threatens this Halloween.
• California faces two distinct scenarios.
• The Southwest could see new flooding.

A corridor of tropical moisture could fuel intense rain in the Southwest during the Halloween weekend and renew flood concerns. According to AccuWeather, a storm from Alaska and another off Washington would draw that moisture into the western United States.

The remnants of Olana, near Hawaii, would contribute to the tropical influx. The evolution will depend on when the storms and moisture meet. If the corridor connects the Hawaiian area with the West Coast, it could set up a Pineapple Express, a type of atmospheric river.

Rain in California: The Most Likely Scenario

🎃 TRICK-OR-TREAT WEATHER: Don’t let a frighteningly soggy forecast put a hex on your Halloween! While the Northeast is in for a spooktacularly dry evening, showers and storms across the South and West look down-right ghastly—so you might need to make an umbrella part of your costume.

— FOX Weather (@foxweather) October 27, 2026

The forecast released on October 27 favors a rapid movement of the systems, which would remain partially separated as they travel along the Pacific coast. This scenario would limit precipitation in Los Angeles, San Diego, and Palm Springs, although it could make travel and outdoor activities difficult. Most major metropolitan areas in Southern California would receive less than one inch of rain, equivalent to about 25 millimeters. Some south- and west-facing slopes could accumulate between one and three inches, approximately between 25 and 76 millimeters.

A Less Likely Scenario Would Increase Flooding

The alternative with greater impact involves both storms merging earlier with the tropical moisture and forming a slower-moving system near California. If this occurs, precipitation would be more persistent and could produce extensive flash flooding from Saturday afternoon to Sunday. This possibility is less probable than the rapid advance scenario, so it should not be interpreted as a confirmed outcome. Even with moderate accumulations, concentrated downpours could cause localized flooding and debris flows in recently burned areas and their surroundings.

Arizona, Utah, Colorado, and New Mexico Face Risks

AccuWeather considers it more likely that the storms and moisture will combine over the western interior, increasing the threat of heavy rain there. Areas of Arizona, Utah, New Mexico, and Colorado could experience flash flooding and significant increases in river levels. Phoenix, Flagstaff, Durango, and Farmington are among the cities that could face downpours from the end of the weekend to the beginning of next week.

YOU MAY BE INTERESTED: California faces historic tides: the sea is already flooding streets and threatening homes

Recent rain has increased the vulnerability of some areas. However, less affected places can also flood if they receive intense precipitation in a short time.

How to Prepare Plans for Halloween

Families with activities planned for Saturday, October 31, should check the local forecast as the celebration approaches. It’s a good idea to have an indoor alternative and check road conditions before traveling, especially near mountains and burned areas. If a road is flooded, avoid crossing it: it’s difficult to gauge the depth, current strength, or pavement damage. The forecast also includes snow in elevated areas of the Rocky Mountains; those traveling to these areas should check pass conditions.

SOURCE: accuweather