It is late summer in the US and I am starting to look forward to autumn and winter mountain biking. I have a carbon fiber frame though. Didn't get to ride it last winter due to a broken collar bone (almost landed that jump). So, anything to be concerned about riding a carbon fiber mountain bike in cool/cold weather? I am talking anything from 50°F/10°C down to sub freezing temps.
Did a quick look around... And Zinn in Velonews gets questions like this. Short answer is: no problem. Essentially carbon fiber is a pretty tough material and barring manufacturing flaws should put up with a lot.
I have been using carbon handlebars on my mtb for two years now with any issue. Even did a race that was so cold that my drink tube froze before I even started!
Many fatbike manufacturers are currently making full carbon frames intended to be raced and ridden at sub zero temperatures. These manufacturers were previously using titanium, but most folks ran all the same carbon parts that everyone else did on their regular mountain bikes. Short answer, yes. This has been done for a long time and the breakage rate hasn't been anything different than normally seen with warm weather riding.