Montrealers would be well advised to bundle up or enjoy the great indoors this week, as a sustained period of bone chilling cold has descended on the city, leading authorities to launch a fleet of vans to ensure that homeless and other vulnerable people are not left outside.

Temperatures are forecast to further plummet after a sunny Monday which saw temperatures rise to about -15 C, as Environment Canada is predicting five days of even more intense cold.

Temperatures are expected to dip far well below average – which usually peaks at about -5C and descends only to about -14C - and New Year’s Eve revelers can brace for temperatures that will likely descend to -22C Tuesday.

Wednesday is not expected to get any warmer than -18C, Thursday will likely top out at-20C and Friday will only -18C before the mercury slowly rises Saturday.

"Dress with whatever you have, layers, layers, layers," said Lise McAuley of CTV Montreal, describing the proper attire to deal with the potentially life-threatening Arctic air mass.   

Matthew Pearce of the Old Brewery Mission said that the group is actively trying to persuade anybody left outside to come on indoors.

“We are going to places where homeless people sometimes tend to congregate and we’ll invite them into the bus and give them a warming up and hopefully that will be preferable to staying outside and hopefully we’ll coax them into coming to the Old Brewery Mission," he said.

City spokesman Jacques-Alain Lavallee said that authorities will also be on the lookout for people who plan on staying outside. Those individuals are often found in such places such the areas near metro station entrances, as well as bus shelters and hospitals.