US polar vortex: Warmer-than-normal weather after 21 die due to deep freeze

Tens of millions of Americans braved Arctic-like temperatures on Thursday as low as minus 56 degrees Fahrenheit (minus 49 Celsius) that paralysed the US Midwest and were blamed for at least 21 deaths.

Warmer-than-normal weather was on the way, but that offered little comfort to vulnerable populations such as the homeless and elderly enduring cold that caused frostbite in minutes and made being outside potentially deadly.

Officials across multiple states linked numerous deaths to the frigid air. The death toll rose from a previous 12 after at least nine more people in Chicago were reported to have died from cold-related injuries, according