With more heavy rain expected overnight -- municipal crews are working overtime to clear catch basins and remove excess snow.

Across Vancouver, works crews were battling the clock to keep catch basins clear in advance of downpour.

"Right now, it's just a matter of being out throughout the whole city and we're trying to free up as many catch basins as we can and also deal with the calls that we're getting from the public," said Murray Wightman of the City of Vancouver. "Through tonight into tomorrow is our biggest concern. We've got people, We've scheduled people now to work through the night."

Rivers under flood watch

Tuesday's heavy rainfall has prompted officials with the River Forecast Centre to issue a high streamflow advisory, meaning rivers and streams could rise rapidly in some areas.

Public Safety Minister John van Dongen said the province will provide sandbags and other resources wherever needed.

But he said municipalities are responsible for having their own emergency programs in place to deal with any flooding.

"The Provincial Emergency (Preparedness) people are involved in conference calls with municipalities and the River Forecast Centre, sharing their most up-to-date information," he said.

Environment Canada said rain is expected to pelt the south coast for most of the week with up to 150 millimetres in the next 48 hours, on the heels of a near-record snowfall last month.

Larger rivers, such as the Chilliwack, Stave, Coquitlam and Seymour will peak Thursday and aren't expected to reach flood stage.

Alan Chapman of the River Forecast Centre told CTV News that the Fraser Valley will be the "bullseye" of the storm.

Roofs collapse under weight of wet snow

And at least five roofs have collapsed in Metro Vancouver because of heavy snow and rain in a little over 24 hours.

A residential roof caved in in Port Coquitlam. Witnesses say the interior of the property could be clearly seen, including furniture.

The roof of a condo project in Burnaby also caved in, and cars were damaged but no one was injured.

"It kind of shifted off sideways and collapsed," said Assistant Fire Chief Ward Rossiter of the Burnaby Fire Department.

In Port Moody, residents of a townhouse complex have been evacuated because of a partial roof collapse.

The snow's been causing trouble for everybody and it got warm pretty quick," said resident Todd Ingram. "I would assume a lot of people are having problems with the weight on the roofs."

And a roof that was being built as part of a house renovation in Vancouver partly collapsed. Police say this was partly due to the weather.

On Monday, the roof over a swimming pool at a Surrey recreation centre completely caved in, but no one was hurt.

Pool supervisor Michelle Vallee said it fell moments after she evacuated the building.

One roofer who spoke to CTV News said the snow was absorbing the heavy rain that fell around the region Tuesday, doubling or even tripling the weight pressure placed on roofs.

Okanagan gets more snow

Meanwhile, Kelowna and elsewhere in the Okanagan were hit by another dump of snow.

Roads were treacherous and conditions forced a two-hour closure of the airport.

With reports from CTV British Columbia's Jina You, Kent Molgat, Stephen Smart and Julia Foy, and with files from The Canadian Press