Historic heat to extreme chill: why is the US experiencing a cold snap?

Blistering cold events are becoming more stark and pose a threat not only to humans but to entire ecosystems

The extreme cold settling over the US this week will be biting, as a blast of arctic air and strong winds threaten to plunge several regions into subzero temperatures. Roughly 150 million people across the US will be forced to face the frigid conditions, posing life-threatening dangers to anyone without shelter from the storms, wreaking havoc on holiday travel plans and possibly straining susceptible power grids.

The shock to the system so to speak - whether that's human bodies or power grid - is going to be substantial because we haven't seen this in a long time," said climate scientist Daniel Swain, noting that, in general, numbing cold is becoming less common.