An Arctic blast, fueled by a collapsing polar vortex, is sending frigid temperatures from Siberia and the North Pole into the Great Lakes region, including Chicago. The National Weather Service has issued an extreme cold warning for central Cook County, effective from 3 a.m. Friday until noon. This warning indicates that wind chills are expected to plummet to between -30 and -35 degrees Fahrenheit, with actual temperatures potentially reaching as low as 1°F on Friday.