Guitars and Humidity
Keep the guitar in an environment with normal humidity. In the winter, with a furnace or radiators running much of the season, humidity is literally cooked out of the air.
Nature loves a balance. In an overly-dry environment, what happens is the woods of your guitar surrender their natural moisture content in a futile effort to humidify your room. And this is Really Bad for the guitar.
The guitar case offers a closed environment where you can easily control the humidity. You can also put a guitar humidifier inside the case. There are many humidifiers available, and any of them will do the trick. It is typically a sponge-type material encased in something like a plastic holder. You keep the sponge part moist and stored in the case along with your guitar.