Ottawa and the rest of eastern Ontario can expect to be plunged into the deep freeze as people head back to work and school.
After an unseasonably warm Christmas holidays, Environment Canada says a frigid air mass could bring temperatures as low as -30 C on early Thursday morning.
On Monday, as the air mass moved in, the temperature was expected to hold at about -15 C, but with the windchill it will feel like -25 C.
The City of Ottawa has issued a frostbite advisory beginning on Monday until further notice.
The temperature Monday overnight is expected to drop to -20 C and rise Tuesday to a high of -10 C, with flurries possible.
On Wednesday, there is expected to be a mix of sun and cloud and possible flurries, with a high of -16 C.
Wednesday overnight and early Thursday morning is when the temperature really drops to an expected -30 C in Ottawa, and -31 C in towns like Pembroke and Petawawa.
The temperature should warm on Thursday to a high of -11 C.
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