Polar vortex

Extremely cold Arctic air and severe winter weather swept southward into much of the U.S. in mid-January 2024, breaking daily low temperature records from Montana to Texas. Tens of millions of people were affected by dangerously cold temperatures, and heavy lake-effect snow and snow squalls have had severe effects across the Great Lakes and Northeast regions. These severe cold events occur when the polar jet stream – the familiar jet stream of winter that runs along the boundary between Arctic and more temperate air – dips deeply southward, bringing the cold Arctic air to regions that don’t often experience it. Surface temperatures at 7 a.m. EST on Jan. 16, 2024. Temperatures below freezing are in blue; those above freezing are in red. The jet stream is indicated by the light blue line with arrows. Mathew Barlow/UMass Lowell, CC BY An interesting aspect of these events is that they...