Despite the deep freeze, many homeless people had still been sleeping in the camp, which housed suitcases of belongings, mattresses and blankets.
Police say every so often they go into Viger Square to remove people and their belonging left in the area.
"Tonight we don't want them to sleep there. They'll have to sleep elsewhere," said Montreal police spokesman Laurent Gingras. "It's also a question of cleanliness, of public health."
Gingras said they mostly pick up garbage and soiled needles.
The belongings that are still usable — such as the blankets and bags — are picked up by a local non-profit group that holds them until the owners come collect them, Gingras added.
There weren't very many people still around when police went to Viger Square this morning, he said, adding that the area is cleared out about every other week — regularly enough for people who stay there to know that this happens.
The City of Montreal released a statement saying it would prefer people slept in a shelter tonight because of the extremely cold temperature.
“We are still trying to convince the homeless that it's for their safety not to sleep outside and direct them to shelters,” read the statement.