Vancouver issued a boil water advisory on Thursday after a powerful storm that left thousands of people without power in southwestern B.C. stirred up water supplies.

Water coming out of taps is cloudy and brown. Two million residents in the greater Vancouver area and its suburbs were told not to drink the water, wash vegetables with it, or even brush their teeth with it without boiling it first.

It is not uncommon for water in the area to gain some colour after a storm.

But a news release from the regional district said turbidity levels this week have reached "levels unprecedented in recent years."

The advisory is a precaution that may last more than a day. Health authorities said there is no evidence of contamination but that the high levels of turbidity raised concerns about stomach illnesses.

CTV's medical specialist Dr. Rhonda Low told CTV News that people don't need to worry if they've already drunk some of the water, because the risk is low and the advisory is a precaution.

If you should start to experience symptoms of abdominal discomfort, bloating or watery diarrhea, see your family doctor, Low said. It can take as long as a week for such symptoms to appear.

A massive repair and cleanup effort is in full swing after violent winds and heavy rains battered the province Wednesday, downing power lines and toppling trees.

Outages extensive

More than 210,000 British Columbians in the Lower Mainland and Vancouver Island region were without power overnight.

About 500 repair crews working on working on power lines across the Lower Mainland, Fraser Valley and Vancouver Island managed to restore electricty to more than half that number by mid-afternoon Thursday, BC Hydro spokeswoman Elisha Moreno told CTV News.

About 80,000 homes were still without electricity early Thursday evening.

"The damage to the infrastructure in the lower mainland and Vancouver Island is fairly extensive, Moreno said. "The magnitude and volume of downed lines is extraordinary."

But the utility is being cautiously optimistic that the majority of customers will have power back on by the end of Thursday night, she said.

The exception is remote areas along the sunshine coast on northern Vancouver Island and the out-lying areas of the Fraser Valley, which may not regain power until late Friday or possibly on the weekend, she said.

Most of the outages were in Surrey, Langley, Abbotsford and Chilliwack on the B.C. mainland, as well as Port Alberni, Campbell River, Parksville and Qualicum on Vancouver Island.

CTV's Janet Dirks, reporting from Surrey, said power was still out there at  6 p.m. EST. Darkened traffic lights were causing gridlock and accidents.

Officials said continuing winds and rain hampered repair efforts on Thursday.

Crews worked to reopen road links after floods, mudslides and downed trees and power lines cut off access.

Accessibility a problem

There are problems reaching some of the more remote communities, Moreno said.

"It is really challenging," said Moreno, noting that 110-kilometre per hour winds and driving rain continued through much of Thursday."

Especially difficult to reach are communities on northern Vancouver Island around Tofino and Ucluelet, she said.

In the Alberni Valley, the only highway connecting the region to the rest of the province was shut down Wednesday, isolating the entire community. By Thursday, Port Alberni Mayor Ken McRae said the situation had improved dramatically and Hydro crews were able to reach the town.

"With the power off and the roads all blocked off coming in and out of the valley it was a pretty scary situation," said McRae.

Emergency shelters were set up for residents needing a place to sleep Thursday after many homes were completely flooded. More than 200 basements filled with water.

In another incident Wednesday, the storm apparently helped knock down a steel-frame building under construction in Vancouver. No one was injured in the incident.

Evacuations

In one community near Horseshoe Bay, about 50 town homes and condominiums were evacuated because of crashing trees.

"Officials estimate more than 100 trees fell through out the storm, CTV's Dave Lefebvre reported. "The problem is now identifying trees left standing that are no longer safe. Workers will have to cut those down, to eliminate any risk they pose to homes below."

Lefebvre said that now officials were worried about a landslide. The wind, rain and falling trees have made a ridge above the town unstable, he said.

The storm dumped between 37 and 80 millimetres of rain on the Lower Mainland, bringing the rainfall total for November to 235 millimetres, and easily surpassing the monthly average of 181 millimetres of rain. The storm put the province on pace to break the 1983 record of 351 millimetres.

Environment Canada has reported that an intense frontal system over the eastern pacific will continue to intensify and hit the south and central coast, spreading heavy rain and strong winds.

Meanwhile, wind gusts forced B.C. Ferries to cancel or delay sailings on major routes connecting the B.C. Mainland to Vancouver Island and the Gulf Islands.

Harbour Air has also cancelled flights from Vancouver to Victoria and Nanaimo, although West Coast Air has kept its flights between Vancouver and Victoria.

Helijet service across Georgia Strait is not affected.

With reports from CTV's Todd Battis, Janet Dirks, Dave Lefebvre, Dag Sharman and files from The Canadian Press