Winter weather with ice, snow, freezing rain and sleet was expected to ramp up by 6 p.m., Roman said, with winter conditions overspreading the entire Chicago area from around 8 p.m. through midnight. Roman noted 6 p.m. through midnight Wednesday was "peak timing" for freezing rain, sleet and icy roads.

A potentially dangerous ice storm is set to slam millions of people from the Midwest to the Northeast starting Wednesday, and that could lead to power outages and treacherous travel from Chicago to Boston.

Freezing rain, sleet and icy conditions are expected to overspread across the Chicago area Wednesday as a winter weather system moves across parts of Midwest and the Northeast.