Temperature change should be gradual.
Optimally, you want to keep your guitar with you, and free from the hazards inherent in any temperature extremes. Of course, this isn't always possible but temperature extremes are more likely when you're traveling with a Voyage-Air Guitar!
In regards to temperature extremes realize that a fine guitar is a collection of different kinds of wood all glued together to produce the complete instrument. When heated all woods expand slightly. This is normal and taken into account when the instrument is designed.
The important point is that different woods absorb heat and expand at different rates. If a guitar is subjected to a sudden temperature change some of the woods will expand or contract much more quickly than others. This results in unnecessary stress to the instrument.
The very worst case scenario is where a guitar is stored for some period in the ice-cold trunk of a car and then immediately brought to play in a warm room. Even worse would be to immediately play it while sitting near a wood stove or a fireplace. The thin wood top of a quality guitar can actually crack from such stress.
If your guitar is ice-cold to the touch give it some time to warm up to the room. Open the case an inch and allow about 15-30 minutes for the instrument to gradually come to room temperature.
A guitar may be safely frozen and thawed without damage. However over time continuous freezing and thawing cycles may result in "spider web" cracks in the finish of the guitar.