The polar vortex is making a painful visit to the Midwest beginning Tuesday. All-time cold temperature records will be set and wind chills will plummet to dangerous levels, with more than 83 million people expected to see temperatures drop below 0°F by week's end.
The big picture: A piece of the polar vortex has spun south, out of its typical home in the Arctic, for a life-threatening sojourn in the U.S. This is bringing ultra-cold weather to at least 15 states, where wind chill warnings and advisories have been issued as of Tuesday morning. Chicago could set a record for its coldest daily high temperature on record, with the high on Wednesday unlikely to edge past minus 15°F, beating the old record of minus 11°F set on Jan. 18, 1994.