At least 250 million people in the United States and Canada have been affected by a fierce winter storm, killing 18 people and knocking out power to hundreds of thousands of homes and businesses, media reports said.

The “bomb cyclone” storm, triggered by low atmospheric pressure, extends more than 2,000 miles (3,200km) from Texas to Quebec.

It brought blizzard conditions to the Great Lakes on the US-Canada border and left more than 1.5 million people in the dark and thousands of flights have been cancelled since Thursday.

Near white-out conditions have been reported in Minnesota, Iowa, Wisconsin, Michigan and Buffalo, New York, where the US National Weather Service (NWS) reported "zero mile" visibility, BBC reported

In Canada, Ontario and Quebec were bearing the brunt of the Arctic blast, with power cut to hundreds of thousands, the report stated.

Much of the rest of the country, from British Columbia to Newfoundland, was under extreme cold and winter storm warnings.

Power systems across the US were under strain due to rising demand for heat and storm-related damage to transmission lines, Al Jazeera reported.

But many electric companies continued to ask people to conserve energy by not running large appliances and turning off unneeded lights.