Weather in Chicago

The 1991 to 2020 normals for Chicago put January at an average high of 31.6F, an average low of 18.8F, a mean of 25.2F, and 11.3 inches of snowfall. The average high is below freezing for the whole month, so an icy platform is the normal condition, not a bad day.

NWS gives a worked example: 0F with a 15mph wind produces a wind chill of -19F, at which exposed skin can freeze in 30 minutes. Waiting on an open elevated platform in a uniform coat with bare hands and no hat is exactly the exposure that example describes.

NWS notes that the areas most prone to frostbite are uncovered skin and the extremities, such as hands and feet, and that people exposed to extreme cold can succumb to hypothermia in a matter of minutes. Gloves, a hat and proper footwear matter more than the coat.

Summer is the opposite problem. July normals on the same 1991 to 2020 basis are an average high of 84.5F and an average low of 66.4F.

Choose Chicago notes the Pedway, roughly five miles of underground walkway serving more than 40 blocks of the Central Business District. In January it is the difference between a walk you can make in uniform and one you cannot.