The Tribune has a graphic up demonstrating how Chicago temperatures dropped 20°C in one day. We went from a high temperature of 28°C at 4pm Monday down to a morning low of 7°C by 7pm Tuesday.
I should mention that I had several windows open Monday night, and closed them around 4am. That helped a little, but it would have helped more had I turned the heat on.
Despite the colder weather, through yesterday I've had six consecutive days of 15,000+ steps, including two of better than 20,000. Today looks promising as well. Fitbit also has a new feature that awards a pip for each clock hour in which you get 250 or more steps, the idea being to get you off your ass. I've got my app set to count from 8am to 9pm. Since Friday, I've had 13 of 13 hours four of five possible days—and today looks pretty likely as well. (The trick is to take Parker for a walk at 5 minutes before the hour, which gets me two pips in 10 minutes.