My coldest ride was a 6.5 km commute, and the temperature that morning was a crisp and fresh -40C/F. By the time I returned home that evening it had warmed up to about -35C or so.

My coldest century was this one ... (click link for story). I was doing a CAM (Century-A-Month) challenge and this was February's ride that year. The starting temperature was -32C/-25F. And no, I didn't bother carrying a bottle after the first lap because it froze solid within about 10 minutes.
http://www.machka.net/brevet/Coldest_Century.htm