Warming centres are being opened across Vancouver for the second night in a row to give homeless residents somewhere to stay as the mercury drops across the region.

An extreme weather alert issued Monday remains in effect, with temperatures expected to feel like -6°C overnight Tuesday factoring in wind chill.

Vancouver opens its warming centres whenever temperatures reach or feel like -5°C as a "life-saving response for people sleeping outside" during the coldest months of the year, the city said in a bulletin.

Centres are being opened at the Britannia Community Centre, West End Community Centre, Powell Street Getaway and the Vancouver Public Library.

The city said anyone is welcome to come inside, and guests are free to bring pets, bikes and carts. Hot drinks and snacks will be provided, and people can sleep if they have bedding.

Up to 100 people used the warming centres on any given night that they were open last year, according to the city bulletin.

Union Gospel Mission is also working to help people out as the nights get colder. Members are already spending 40 hours a week driving around in the Mobile Mission, which is stocked with scarves, gloves, sleeping bags and survival gear.

People working on the front lines know all too well that lives are on the line when temperatures drop, said the UGM's Jeremy Hunka.

"We've seen people die in the cold before, and we've seen people light a candle in a tent that starts the tent on fire," he said. "There's always a risk of putting on a heater that can start a fire or poison somebody inside."

While there aren't any more -5°C nights in the forecast this week after Tuesday, that can always change. The City of Vancouver said the warming centres will be extended if necessary.

Anyone looking for shelter space can call 211 to check availability.

With files from CTV Vancouver's Angela Jung and Ben Miljure