OLYMPIA, Wash. -- A powerful series of storms packing drenching rains and howling winds has killed five people in Washington.

Gov. Christine Gregoire said that in addition to two fatalities reported Monday afternoon in Grays Harbor County, a third man was killed in Mason County on Monday night when a building was hit by a mudslide.

Tuesday morning rescuers found an injured man and the bodies of two hikers who disappeared near Snow Lake near the Alpental ski area in the Alpine Lakes Wilderness area of Snoqualmie Pass.

A Bellevue couple and a friend -- all in their 30s -- were hiking on Saturday when an avalanche buried them, officials told KIRO 7 Eyewitness News reporter Alison Grande.

One man was able to dig himself out, but he couldn't find his wife and his friend. He crawled to his tent, where searchers found him Tuesday morning.

Meanwhile, Interstate 5 -- the main north-south highway in Western Washington that connects the Seattle area with Portland, Ore. -- is closed in Lewis County because of flooding. Water over I-5 is 10 feet deep. The impact on lost business from delayed truck traffic is estimated at $4 million a day, officials said.

Rescue helicopters plucked stranded people from an area near Rochester, in Thurston County. Chopper 7 shot video of the rescue of a Mennonite family at midday on Tuesday. See story, with video of the rescue.

Coast Guard officials in Seattle said the service's helicopters had rescued at least 130 people from areas surrounded by water -- in some cases from rooftops.

Gregoire, who declared a state of emergency Monday, touched down during a helicopter tour of flood damage in Southwest Washington to meet with victims seeking shelter at a Chehalis high school.

She gave them some words of encouragement and told them it was hard to comprehend how deep the water was until she saw it -- in some neighborhoods, the water was up to the rooflines.

The governor's helicopter flew over Lewis, Grays Harbor and Mason counties so far. In one area a Wal-Mart appeared as an island, its parking lot swamped by several feet of water.

The series of storms hit hardest on the Olympic Peninsula, Kitsap County and the southwest corner of the state. Rob Harper, a state emergency management spokesman, said at least 73,000 Western Washington residents were without electricity at some point Monday and more than 50,000 were still in the dark Tuesday.

SLIDESHOW: Viewer-Submitted Storm Photos

Four other hikers stranded by harsh weather were rescued from the Snoqualmie Pass area in the Cascade Range, officials said.

Grays Harbor County sheriff's Detective Ed McGowan and Hoquiam Police Chief Jeff Myers confirmed the deaths of two men, one in Aberdeen who was hit by a falling tree as he was trying to clear another downed tree and one in Montesano who apparently relied on oxygen equipment that stopped operating after electricity was lost.

The National Weather Service said 3 to 6 inches of rain fell across much of Western Washington. The 24-hour rain total for Bremerton was 10.78 inches, meteorologist Chris Burke said Monday evening. The day was the second wettest on record in Seattle with nearly 5 inches of rain in a 24-hour period.

SLIDESHOW: Car Slides Off Golden Gardens Road

A number of sewage treatment plants were overwhelmed, including one in downtown Olympia, causing millions of raw sewage to be released into Puget Sound. It was the first time in 16 years that all wastewater entering the plant could not be treated.

Water systems also were damaged in some areas, including Montesano, where the reservoir was damaged by falling trees and about 4,700 people were advised to boil their tap water if anything appeared to be amiss.

State Ecology Department officials recommended that people avoid water in Puget Sound and adjacent marine waterways for at least a week after the rains subside.

Mudslides blocked numerous roads and forced an undetermined number of residents to evacuate condominiums, apartments and houses in Seattle, at least nine houses in suburban Burien and several mobile homes in Shelton.

Other than I-5, major road closures from flooding and slides included numerous stretches of U.S. 101 along the coast and the Olympic Peninsula and U.S. 12 east of Aberdeen.

Mudslides halted Amtrak passenger train service between Portland and Vancouver, British Columbia, for a second day Tuesday.

Much of Grays Harbor County on the southern Washington coast was without electricity. A Bonneville Power Administration feeder line to the Aberdeen-Hoquiam area was down, and authorities were hoping to arrange for emergency generators that would enable supermarkets in Aberdeen to reopen Tuesday.

Roads leading into the county's population centers were closed or blocked until a patched-together route from Olympia to Ocean Shores was punched through late Monday. Further travel problems were expected as the flood crest moved down the Chehalis River higher and faster than anyone could remember, Myers said.

"Washingtonians have endured quite the weekend," Gregoire said, adding that the flood danger was likely to persist into Thursday. Her emergency declaration put thousands of National Guard troops on standby if local officials need help.

Winds gusted to 81 mph in Hoquiam, next to Aberdeen, early Monday before the National Weather Service line went down. A weather spotter reported winds of 60 mph gusting to 90 mph at 5 a.m. at Clallam Bay on the northern coast of the Olympic Peninsula.

The Elwha River on the northern Olympic Peninsula was expected to flood at record levels. Major flooding was predicted on the Tolt and Snoqualmie rivers near Carnation, east of Seattle.

Flood warnings also were issued for numerous other rivers. Rain-saturated soil also increased the risk of landslides, the weather service said.

In Olympia, the rain turned a normally small creek into a roiling, muddy surge of water that tore through a wall at the Ranch House BBQ. Tables and booths were strewn across the street, and a storage shed was pushed about 300 feet away.

Christy Romo, who lives just up the hill from the restaurant, said she could hear the floodwaters coming and started packing before the first floor of her cabin was inundated.

"I knew I wouldn't have much time," Romo said. "I heard a bang, and then saw the water rising quickly."

Get state road closures information from the Department of Transportation's Web site.