DO NOT expose your guitar to hot temperatures. no hotter than 80 degrees. Prolonged exposure to hot temperatures, especially dry humid conditions, can cause the fretboard to crack and pop up.
Cold air is just as harmful as hot is. If your guitar is exposed to cold conditions for a prolonged period of time and suddenly brought into warm air, this can cause serious damage to the guitars' paint finish and many other problems such as the glue becoming dry and cracking.
In final analagy, the best thing to do is to keep your guitar in the same type of environment year round.
