The only issue I see here is that the computer may get warm enough to make thermal stress a real threat. The higher the temperature difference between operating temperatures and the ambient air, the worse the stress may be. But I'm no materials science engineer so who knows?
Another issue may be with electrolytic caps. The electrolyte is technically a liquid so it may freeze if it gets too cold and may either not work or not work as intended. But I don't know what this temperature is and there probably isn't some magical number. .
So here goes my first post!
I'm a noob in building computers...did build one in 6th grade for school with a bad ass teacher but that was 13yrs ago.
I am familiar with materials/ceramic engineering from studying metallurgical engineering...though never finish metallurgy due to a change of interest.
The worst thing i would try to prevent at cold temps is a SUDDEN/QUICK change in temp. That will cause stress fractures or microfractures in most solid mateials with quick temp changes(mainly either extreme heat to extreme cold or the other way)
I wouldn't worry as long as the lower and upper temp ranges dont very quickly once achieved.
Try to prewarm the computer before booting up.
I'm not as familiar with fluid engineereing but i would treat the caps like batteries, though i don't know their lower temp function either. My iPod wouldn't turn on at -20F but that may be irrelevant.
Look out for my noob questions soon on a new computer build haha