Tens of thousands of people are without power and flights have been grounded at Colorado’s Denver International Airport for much of Monday (local time) as the US region dug out from one of the most powerful late-winter blizzards in two decades.

The heavy storm punished parts of Colorado and Wyoming with up to a metre of snow and wind gusts of more than 70 km/h at the weekend, stranding motorists on major highways and knocking down trees and power lines.

Denver International Airport, which halted all inbound and outbound flights on Sunday afternoon (local time) after 60 centimetres of snow fell on runways, reopened them midafternoon on Monday.

Airport staff gave blankets and water to the roughly 500 passengers that were left stranded at the airport overnight, the Denver Post reported.

State government offices in Denver and surrounding suburban counties remained closed on Monday.

Interstates 70 and 25, two of Colorado’s main arteries across the state, were shut down on Sunday afternoon, along with Interstate 80, which runs east-west across Wyoming. Motorists were advised to stay off the roads on Monday.

Wyoming state offices in the capitol, Cheyenne, would remain closed through Tuesday, Governor Mark Gordon said on Twitter.

More snow was expected across the Rockies on Monday evening and into Tuesday, although National Weather Service forecasters expected it to be considerably lighter and wreak less havoc.

The weather system bringing blizzards to the Rockies was also responsible for severe thunderstorms in Texas at the weekend, including reports of multiple tornadoes on Saturday in the Texas Panhandle.

-AAP