Environment Canada issued a special cold weather statement Sunday. Temperatures are expected to drop at least five degrees below seasonal normals.
Temperatures in Prince George and Fort St. John are forecast to dip down to -22 degrees Celsius.
CBC Meteorologist, Johanna Wagstaffe said, "Our cold air is coming courtesy of a huge arctic high pressure system that is ushering winter in for much of the country this week.
"As cold air is funnelled east across B.C, it blocks out the warmer Pacific air that usually keeps us mild," she said.
However, skies are expected to remain clear and sunny in the afternoons with fog patches in the morning.
Wagstaffe says this "cold but clear pattern" will last through to the weekend. Overnight lows are expected to drop below zero by mid-week in Metro Vancouver.
Vancouver city councillor Kerry Jang says preparations are underway to help people living on the streets find a place to stay.
"Because we have so many outreach workers out in the street right now looking for homeless people asking them how they're feeling and what they want," he said.
Jang explained, "That's usually the best indication when the homeless start saying, 'I want to come inside it's really cold,' that's when we now we have to ramp it up."
He says there are existing heat shelters and more spaces will open up depending on need.
"We expect to get as many people inside as we can," said Jang.
Organizations that provide assistance to homeless people are also gearing up and making preparations.
The Union Gospel Mission in Vancouver, which helps people in need, is receiving 5,000 pairs of underwear today as part of a national campaign through organizations GotGinch and NeedKnickers.