By David Schwartz

PHOENIX (Reuters) - Torrential rains drenched much of the U.S. Southwest on Monday, prompting flash-flood warnings across four states and taking the lives of two women washed away in separate incidents in Arizona.

The Phoenix area was hit by a record downpour that closed sections of two major freeways, and the National Weather Service issued flash-flood warnings for parts of Arizona, California, Nevada and Utah.

"This is a life-threatening situation," the NWS said in an advisory.

In Phoenix, a record-setting 3.29 inches of rain fell on Sky Harbor International Airport, beating the 2.91 inches seen in September 1939 for the city's most rainfall in a single day.

One community on the southeast of Phoenix saw more than 5-1/2 inches of rain.

Arizona Governor Jan Brewer declared a statewide emergency for the affected areas. "If you must travel, please do so with caution & BE SAFE!" Brewer said on Twitter, using the hashtag #TurnAroundDontDrown.

The downpour turned some highways into lakes, with officials saying parts of both Interstates 10 and 17 were shut to traffic. A section of Interstate 15 in Nevada was closed too.

Arizona television stations broadcast footage of some abandoned cars nearly completely submerged. Authorities said several people were rescued from vehicles, and that the roof of a grocery store partially collapsed.

At its peak, airport officials reported flights at Sky Harbor were delayed for 25 minutes. Some 20,000 people were without power across the Phoenix area. Multiple schools canceled classes for the day.

A 76-year-old woman died in Pinal County just south of Phoenix after she and her husband tried to cross a flooded wash.

Their car got stuck, and while the man reached the shore, his wife was swept away, the local sheriff's office said.

Farther south in Tucson, authorities said a woman in her 50s was killed when her car was swept downstream after becoming stuck in a rain-swollen creek.

The Tucson fire department said the woman's vehicle was stuck against a pedestrian bridge, entirely submerged. A crew immediately began getting equipment for a rescue when the car was pushed under the bridge, it said.

Thirty minutes later, the waters receded and the car was found three blocks away, pinned against a concrete tunnel along with trees and other debris.

Weather officials said Tucson also set a single-day record with 1.26 inches of rain dumped at Tucson International Airport. That broke the record of 0.94 of an inch from 1919.

Trooper Chelsea Webster of the Nevada Highway Patrol said a portion of Interstate 15 linking Las Vegas to Arizona was closed in the Moapa Valley because of flooding, and emergency workers were plucking stranded motorists from their cars.

There was no immediate word of any injuries, or how many people had to be rescued from the interstate.


(Reporting by David Schwartz; Additional reporting by Cynthia Johnston in Las Vegas; Editing by Daniel Wallis, Sandra Maler and Peter Cooney)