These maps show the pre-Christmas storm sweeping across Canada

Western Canadians enjoying unseasonably warm temperatures are in for a rude awakening.

An Alberta Clipper is bringing a huge dump of snow to the Prairies and portions of northern Ontario, followed by a waft of frigid Arctic air.

Portions of southern Saskatchewan and Manitoba will see blizzard conditions starting on Wednesday morning, which Environment and Climate Change Canada (ECCC) says will make travel “dangerous and likely impossible due to near-zero visibility.”

Regina and other parts of Saskatchewan are also expected to get freezing rain before the storm transitions to snow, making travel extra treacherous.

Snow accumulation forecasting from ECCC for the next three days shows a band stretching across the Prairies, across northern Ontario, Quebec and Newfoundland and Labrador.

ECCC's forecast also shows large swaths of the country will quickly plunge into frigid weather. Regina will see a low of –23 C on Wednesday evening and Winnipeg will see –19 C.

The federal weather agency has also issued a cold warning in parts of the northern Prairies due to wind chills making temperatures feel as cold as –45 C.

This map shows how that Arctic air will swoop south over the next two days.

This weather is bringing serious warnings from ECCC.

The agency issued yellow and orange weather alerts for most of Manitoba and Saskatchewan on Tuesday.

Canada’s weather agency recently changed its warning system to be colour-coded. Yellow is common and localized weather events; orange is severe, widespread and uncommon events; and red is very dangerous and rare events with extreme and prolonged impacts.

And a reminder: winter doesn’t officially start until Sunday.