i've oways tod its the string
cz strings = metal
metal more sensitive to temperature changes, so the effect is faster
cold shrink, notes sharp
hot expand, notes flat
wood are more sensitive to moisture
like axis, stingray necks, warwick necks, which have very thin finish
since wood are more expose to the air
change of humidity is can cause the neck to react....
many warwicks failed to the humidity

i see bodom using the same guitar for the whole concert 

for the metal in strings to expand or contract by a significant amount, the temperature would have to be very close to 100C...you will die first.
likewise for it to contract, has to be close to 0 or below.

whereas the glue in woods, that is a different story.
any slight melt of the glue and the wood can shift etc.

moisture of cos is the other one causing the wood to shrink or expand.
thats why never ever take out ur guitar from a gig bag or case immediately after going from a hot->cold room or vice versa.
let it rest at least 10mins in the new room.

in a cold room, let's say 16°C, take the guitar and tune it right away... you'll feel that the higher strings are really cold.
once the guitar is tuned, start playing.. the bends, the slides, the friction.. all those are going to warm up the strings and your quitar becomes out of tune in a matter of minutes !

Therefore, the strings do expand and shrink quite happily with temperature ! They heat up to about 25°C/30°C I'd say. --> the tuning is getting flatter.

The rod inside the neck is also made of metal, but (as written earlier) it's protected by the wood... so the impact of T is taking more time. Yet, after a while, the rod will get warmer (if the room gets warmer), therefore more tension --> it will pull the head backwards --> more tension of the strings. The tuning is should be getting a bit sharper. However, i never noticed this...

The wood is not affected by heat (as far as i know !)
The glue... mmm... i'm not sure. If the glue becomes a little less sticky every time the t°C is getting higher, the neck will just snap away after a while, no ?