A powerful storm has spawned tornadoes in South America and brought heavy snow and other extreme weather to parts of the US and Canada.
The storm has injured several people and damaged buildings in Texas.
According to FlightAware.com, about 9,000 U.S. flights were delayed Monday and Tuesday due to storms across the country.
The weather has also closed roads in some western states where up to 2 feet (60 cm) of snow is expected.
Experts said the storm could affect residents of nearly every state in the contiguous United States.
“This is a pretty powerful storm system,” said Rich Otto, a meteorologist with the Weather Prediction Center. “It’s a little bit bigger than your average winter storm.”
“People should stay indoors during the day [Tuesday] if they live in the north,” he added.
Mr. Otto said the worst of the weather began Monday night and was expected to continue through Wednesday, hitting the central and northern High Plains, an area of the United States that includes eastern Montana, Wyoming, southern Includes Dakota and Nebraska.
Wind gusts of more than 40 mph (64 km/h) and heavy snowfall are expected in these states.
More than 20 million people in the US were under severe weather advisories on Tuesday.
A National Weather Service blizzard warning was in effect for all of those states, as well as Colorado. They are triggered by winds of at least 35 mph along with heavy snow.
Mr Otto said heavy snow combined with strong winds would create low visibility and “treacherous” travel conditions.
Snowfall of one to two inches per hour is expected in parts of the region.
The storm has also spread across Canada, with heavy snow and strong winds Tuesday and Wednesday across the country’s southern Prairie region, including the provinces of Saskatchewan and Manitoba.
