The stickers usually give you operating temperatures. Assuming its not going to get rained on (it would in our shed :) ) the worst that could happen is dampness on the circuit boards. A long spell in the warm can usually sort damp circuit boards as long as they dont have power put through them when wet.
Not unless we have the coldest winter for a long time its unlikely to freeze in your shed so it will probably be fine though I personally wouldnt "just in case"
I dont know about yours but our loft gets bloody cold in the winter and its never done any of my PC stuff or TVs any harm.