As a runner, training on the paths and streets of Chicago, you are an outdoorsman, monitoring the elements and dressing accordingly.

The winter rule-of-thumb for acceptable minimum running conditions is:
Temperature Above Single Digits and
Wind Below Double Digits
(Worse-case-scenario 10 Degrees and 10 Miles Per Hour

Other factors include the direction of the wind
as well as any precipitation

We recently experienced a 20 Degree Temperatures coupled with 20 Mile Per Hour Wind Speed directly in our face. At critical points of the ride where the street climbed over expressways and the air seemed funneled over the top the of the rise,

As we neared the top of the crest, facing the maximum wind speed, it almost stopped us (as if on some gym-machine or training cycle set for maximum resistance)
We barely crawled forward, tempted to stop and walk the bike, almost in tears

The reward was that we arrived at home, even before alternative transportation, would have just departed from downtown on its trip north