If your guitar doesn’t have a humidifier in the case get down here and buy one. Furnaces take moisture out of the air, which takes moisture out of wood, resulting in screwed up guitars. Fingerboards shrink and fret ends will shred your fingers, bridges pull off of acoustics, necks warp, wood cracks. etc. and a whole host of problems can and will arise. Is your guitar a cheapy? Doesn’t matter. Have a wonderful expensive instrument? Doesn’t matter. Get in and buy a humidifier. Econo Herco humidifiers run a mere $5.50 and the truly superior ones from Oassis are $20.00. What are they worth? Plenty if they save your instrument from turning into the guitar version of a raisin.