The south coast of British Columbia is getting another blast of winter just in time for Christmas, with as much as 30 centimetres of snow forecast to fall by midnight Wednesday.

A snowplow heads out on the roads in Vancouver as a storm approaches the south coast of B.C. Tuesday night. (CBC)

The storm is the latest during a two-week cold snap, and residents are again being warned to brace themselves for major airport delays, treacherous roads, transit stalls and power outages.

In downtown Victoria on Wednesday morning, the precipitation was falling as rain, but it was snowing heavily elsewhere on the south coast as the temperature hovered around 0 C.

The snow was expected to continue through Thursday morning, before temperatures warm up with possible sunny breaks in the afternoon, making it the whitest Christmas in 50 years for the south coast of B.C.

The precipitation will turn to rain on Friday, with highs of 8 C forecast for the weekend likely to melt much of the snow.

Elsewhere in the province, snow was forecast for the southern Interior as the storm moved east on Wednesday, while temperatures as low as –29 C were forecast for Fort Nelson in northern B.C.

Air Canada cancels many flights

The heavy snow was causing problems at south coast airports during the busiest travel day of the year, with more than 70,000 holiday travellers scheduled to pass through Vancouver International Airport alone.

Flights were delayed or cancelled once again at Vancouver International Airport on Tuesday. (CBC)

Officials at the Vancouver airport were reporting crews were managing to keep both runways open, but dozens of flights were listed as cancelled or delayed.

Air Canada announced it was cancelling all flights to parts of B.C. and Western Canada and the West Coast of the U.S. out of Vancouver on Wednesday, but the airline was attempting to maintain departures to Eastern Canada and overseas destinations.

Air Canada also cancelled many flights out of regional airports on Wednesday, including Victoria, Kamloops, Kelowna.

Customers holding tickets to cancelled flights were advised not to head to the airport until they rebook their flight through the telephone reservation system.

The airline was blaming weather and reduced airport operations for the cancelled flights, but airport officials told CBC News the airline is struggling with staff shortages.

Meanwhile WestJet flights were delayed, but few appeared to have been cancelled, and most international flights, including those heading south to sun destinations, appeared to be the least affected by the delays.

People planning to travel Wednesday were advised to check their airport's website or call their airline, but at 9 a.m. PT the airport website was only working intermittently.

The delays and cancellations come just as the airlines struggle to clear a backlog of passengers from weekend snowstorms that left thousands of passengers stranded at airports across B.C. and Canada on Monday and Tuesday.

Metro Vancouver transit delays

In Metro Vancouver at 8 a.m., both the Millennium and Expo SkyTrain Lines were experiencing delays and the West Coast Express was blocked by a stalled train. TransLink was sending buses to help commuters get to their destinations.

A bus struggles to make it up a hill in Vancouver on Tuesday. (CBC)

On the roads, conditions were slippery, but traffic was light. About a dozen tractor-trailer tracks were blocking Knight Street in Vancouver.

TransLink ran trolley buses throughout the night to keep the overhead lines clear of snow and ice, but many buses were struggling on routes with snow-packed hills.

Buses on Oak Street were not running at 9 a.m. PT and were being rerouted to Granville Street, while HandyDART service was restricted to essential dialysis and priority medical trips only.

TransLink was advising anyone using public transit to dress warmly and be prepared for long waits.

Malahat reopened, power out on the islands

On Vancouver Island, the Malahat section of the Island Highway, near Goldstream Park, reopened at 9 a.m. PT after crews cleared a tree that came down on a tractor-trailer.

No other highways were closed as of 8 a.m., but conditions were expected to deteriorate as the snow continued to fall.

About 16,000 BC Hydro customers on the south coast were without power by 8 a.m., mostly because of lines brought down by trees and snow.

Affected areas included large parts of Richmond, Delta, Burnaby, Coquitlam, New Westminster, Victoria, Saanich, Duncan, Campbell River and Vernon, as well as Galiano, Pender and Mayne islands.

Several hundred customers in Vernon in the Okanagan also lost power Wednesday morning.

All the heavy snow was also raising the risk of avalanches, particularly on the south coast, where the risk condition was upgraded to "considerable" for the alpine area of the Sea to Sky region.