At least 20 dead as millions in US endure record cold without power

Traffic in Austin, Texas. (Jay Janner/Austin American-Statesman via AP)

A winter storm that left millions without power in record-breaking cold weather has claimed more lives, including three people found dead after a tornado hit a town in North Carolina and four family members who perished in a Houston blaze while using a fireplace to stay warm.

The storm that overwhelmed power grids and immobilised the Southern Plains carried heavy snow and freezing rain into New England and the Deep South and left behind painfully low temperatures. Wind-chill warnings extended from Canada into Mexico.