The polar vortex is coming back — and that's bad news for northwestern Ontario, which saw some record-breaking low temperatures earlier this month.
Environment Canada meteorologist Jeff Coulson said the same kind of system will head south, from the Arctic, next week.
"We are seeing a pipeline setting up of very, very cold Arctic air, starting in the far north of the country," he said.
"[It will be] working its way down, almost due north to south ... through northern Ontario, and then deep down into the U.S. as well."
Coulson said a number of Canadian and U.S. weather forecast models all call for colder-than-seasonal temperatures in their seven- and 14-day outlooks.
The coming deep freeze looks to be a long-lasting one.
"On Monday, Thunder Bay will struggle to get a a daytime high of -17 C. The normal should be about -9 C. Those temperatures [will be] staying around those values for much of the rest of next week," Coulson said.
"We may get a few more days over the course of the next few weeks with more seasonal temperatures, but the overall trend is for much colder-than-normal temperatures, right through the northwest, to finish off January and to start the month of February."
Over the short term, the area may experience lows of -30 C or colder, he added.
The seven-day forecast for Thunder Bay calls for overnight lows of -24 C to -29 C until Thursday.