Indianapolis: Dangerously cold polar air snapped decades-old records as it spread on Tuesday from the Midwest to southern and eastern parts of the US and eastern Canada, making it hazardous to venture outside and keeping many schools and businesses closed.
Monday's temperatures broke records in Chicago, which set a record for the date at minus 16 Fahrenheit (minus 27 Celsius), and elsewhere.
In Toronto, a message on Pearson International Airport's official Twitter account Tuesday morning said "extreme cold (is) causing equipment freezing and safety issues for employees. Ground stop in effect until at least 9 a.m."
Forecasters said some 187 million people could feel the effects of the "polar vortex" by the time it spreads across the US.
Even the South was startlingly cold. Temperatures plunged to 8 degrees (-13 Celsius) in Atlanta.
PJM Interconnection, which operates the power grid supplying energy to more than 61 million people in parts of the Mid-Atlantic, Midwest and South, asked users to conserve electricity Tuesday because of the cold.
More than 15,000 customers in Indiana remained without power.
More than 500 Amtrak passengers spent the night on three stopped trains headed for Chicago because of blowing and drifting snow in Illinois.
Bob Oravec, a meteorologist at the Weather Prediction Center in College Park, Maryland, said the blast of frigid air raised concerns that roads wet from melted snow from a weekend storm would freeze over.
But there are signs things were returning to normal. Warmer temperatures -near or above freezing - were forecast for the Midwest.