OLYMPIA, Wash. — Drenching rain and howling winds that downed trees, cut electricity and caused widespread flooding have left two people dead and closed a the main north-south highway in Western Washington.

Gov. Chris Gregoire declared a state of emergency Monday following the third in a series of storms that hit hardest on the Olympic Peninsula, Kitsap County and the southwest corner of the state. Gregoire said about 80,000 Western Washington residents were without electricity.

Coast Guard and Navy rescue helicopters were dispatched to rescue people stranded at their homes by heavy winds and flooding, officials said.

By 10 p.m., six Coast Guard helicopters had hoisted 66 people from areas surrounded by water — in some cases from rooftops, said Petty Officer Kelly Parker in Seattle.

About 150 people were stranded at some point across the region, Gregoire said, and about half reportedly had been rescued by Monday evening, some by boat. Four hikers stranded by harsh weather were rescued from the Snoqualmie Pass area in the Cascade Range, officials said.

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.

Interstate 5, the principal north-south route along the West Coast, was closed near Centralia because water was about 3 feet over the road. The last time flooding closed I-5 at that location was for four days in 1996. If the Chehalis River crests Tuesday at nearly 75 feet as expected, I-5 will be under about 5 feet of water, state Transportation Secretary Paula Hammond said.

“Once it’s over the axles, you’re pretty much in danger of getting stuck in the water,” state transportation engineer Peter H. Craig told KIRO Radio of Seattle early Tuesday.

The freeway will remain closed at least through Wednesday, and “it could well be longer than that if we’ve had some road washout,” Craig said.

Elsewhere in Lewis County, emergency crews labored through the night to monitor and rescue people trapped in houses.

Boats were used by day and global positioning system-equipped helicopters took on a bigger role after dark, in some cases plucking people from the roof of a house, sheriff’s Detective Matt Wallace said.

No fatalities were reported in the county and one case of hypothermia was the only notable injury, Wallace said.

Two Coast Guard helicopters, one each from Astoria, Ore., and Port Angeles, were used to rescue about 40 people stranded by flooding early Tuesday, mostly from Centralia about 40 miles west to Pe Ell in the coastal hills, sheriff’s Sgt. Stacy Brown said.

A dike along the Chehalis River by Long Street west of downtown Centralia may have broken overnight, but it was too dark to tell for certain whether it failed or water was pouring over the top, Brown said. The problem was in a different area from a dike break in 1996, she added.

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 today.

Much of Grays Harbor County on the southern Washington coast was without electricity.

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.

Grays Harbor County sheriff’s Detective Ed McGowan, the county’s incident commander for the storm, confirmed two deaths — a man in Aberdeen who died when a tree fell on him as he was trying to clear another downed tree, and someone who died of an undetermined medical problem after power 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.

“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.

Lewis County residents in flooded areas were urged to evacuate and several shelters were opened. 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.

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.

The governor reminded drivers to avoid all flooded areas and residents without power to avoid using electric generators or barbecue grills indoors because of the danger of carbon monoxide poisoning, Gregoire 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.”