By Eric M. Johnson

SEATTLE (Reuters) - At least three people were killed and about 250,000 homes and businesses were without power in Washington state on Wednesday after a storm blew down trees and triggered mudslides, authorities said.

A wide swath of the Puget Sound region was under flood watches and warnings through Wednesday afternoon, the National Weather Service said.

In the Spokane area of eastern Washington, utility Avista said nearly 115,000 customers were without power and the city closed schools on Wednesday after winds up to 70 mph (113 kph) tore through the area.

In Oregon, fallen trees, mudslides and floods shut down roads across the western part of the state on Tuesday night, including a 50-mile (80-km) stretch of Interstate 84 that authorities declared impassible into midday Wednesday. Several other highways remained closed, Washington state police said.

At least three people were confirmed to have died in storm-related accidents, authorities in Washington state said.

A motorist was killed on Tuesday near the city of Monroe, northeast of Seattle, when a tree fell from a cliff onto his car, said Snohomish County Fire Chief Merlin Halverson.

"Many roads are closed from downed trees, active power lines, flood waters," Halverson said. "It's a hell of a mess here."

In Spokane, police said a woman was killed by a falling tree while another woman died on State Route 904 southwest of the city when a tree struck her car, state police said on Twitter.

Puget Sound Energy, which supplies customers in parts of Seattle and its suburbs, reported roughly 70,000 outages on Wednesday morning, down from about 210,000 late on Tuesday.

To the north, in Snohomish County, the public utility district said about 65,000 customers were without power on Wednesday morning, compared with 150,000 the night before.

Mudslides and other debris blocked state and U.S. roads in parts of the state.

King County, home to Seattle, reported severe flooding on the Snoqualmie River, moderate flooding on the Green River and minor flooding on the Cedar River.

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An airport in Olympia received 2.08 inches of rain on Tuesday, a record for daily precipitation, the National Weather Service said. The previous record was 1.61 inches set in 1959.

The Seattle-area was due to see scattered showers and some sunshine on Wednesday, the service said.

(Reporting by Eric M. Johnson in Seattle; Additional reporting by Courtney Sherwood in Portland, Oregon, and Victoria Cavaliere in Los Angeles; Editing by Daniel Wallis and Bill Trott)