VANCOUVER - It's shaping up to be a dark Christmas for thousands of households in southwestern British Columbia.

BC Hydro crews have been working around the clock to restore service since a powerful windstorm swept through the region on Thursday.

The utility says it has reconnected more than 550,000 customers, but as of early Monday morning just under 26,000 remained in the dark - most of them on Vancouver Island - and it could be three more days before power is restored to rural areas.

BC Hydro said the storm was one of the worst it had seen in 20 years.

RCMP say it killed a woman in Duncan when it blew a tree down on her tent. It also shutdown Nanaimo's water treatment plant, and it destroyed a 30-metre section of White Rock's pier.

Vancouver Island and the Gulf Islands were among the hardest hit areas, with hundreds of downed trees blocking roads and preventing hydro crews from completing full damage assessments.

The province's public safety minister, Mike Farnworth, said emergency operations centres have been activated in affected areas and warming centres have been opened in many communities.

Some of the damage on Salt Spring Island seen below: