The mystery of my desktop that locks up when it gets too cold

This winter I have been having a sporadic but surprisingly consistent problem with my home desktop computer, which is that, well, here’s my Tweet:

What has been happening sporadically all winter is that when the ambient temperature around my home desktop drops too low, the machine will lock up. When the ambient temperature rises again, the machine boots up again. One time I deliberately created a low temperature situation where I could see the machine in this state after it had locked up, before the temperature rose again and it came back to life.

Source: utcc.utoronto.ca