TROPICAL STORM HILARY was accelerating northward off Mexico’s Baja coast today, no longer a hurricane but still packing what forecasters called “life-threatening” rain likely to unleash flooding across a broad region of the western US.

As of 8am Pacific time (4pm GMT), Hilary was located about 350 kilometres south-southeast of San Diego, the National Hurricane Centre reported.

Hilary had maximum sustained winds of 110 kmph and was moving northwest at 40 kmph, remaining just off the Pacific coast.

The Mexican cities of Ensenada and Tijuana, directly in the storm’s path, closed all beaches and opened a half-dozen shelters at sports complexes and government offices.

Residents pull wagons with sandbags in Long Beach Damian Dovarganes / AP Damian Dovarganes / AP / AP

Hurricane Centre director Michael Brennan said that while Hilary had weakened from a Category 4 hurricane, it is the water, not the wind, that people should watch out for most.

“Rainfall flooding has been the biggest killer in tropical storms and hurricanes in the United States in the past 10 years and you don’t want to become a statistic,” Brennan said in an online briefing from Miami.

Forecasters expected Hilary to make history as the first tropical storm to hit Southern California in 84 years, bringing flash floods, mudslides, isolated tornadoes, high winds and power outages.

Tropical storm and potential flood warnings were posted for the entirety of Southern California, from the Pacific coast to interior mountains and deserts, and as far north as eastern Oregon and Idaho.

Hilary was expected to remain a tropical storm into central Nevada early tomorrow before dissipating.

Brennan said rainfall could reach between three and six inches (7cm and 15cm) in many areas, with some higher amounts in isolated spots. Forecasters warned it could dump up to 10 inches (25cm) — a year’s worth of rain for some areas.

Lifeguards fill up sandbags for residents in Long Beach, California

California governor Gavin Newsom declared a state of emergency.

The Federal Emergency Management Agency said it has officials inside California’s emergency preparedness office and teams on standby with food, water and other help.

Hilary is just the latest major climate disaster to wreak havoc across the US, Canada and Mexico.

Hawaii’s island of Maui is still reeling from last week’s blaze that killed over 100 people and ravaged the historic town of Lahaina, making it the deadliest US wildfire in more than a century.

Firefighters in Canada are battling blazes during the nation’s worst fire season on record.

Hilary left a long string of washed-out highways and roads up and down the Baja peninsula in its wake today.

Some of the worst damage occurred in the coastal towns of Mulege and Santa Rosalia, on the east side of the peninsula, where a man died on Saturday after his family’s vehicle was swept away by a swollen stream.

Four other occupants of the vehicle were rescued.

Power lines were toppled in many places, and emergency personnel were working to restore power and reach those cut off by the storm.