Wood is hygroscopic, which means its MC (moisture content) will fluctuate based on the relative humidity (RH)of the surrounding air. As humidity increases, the MC increases, and the wood expands, and as the humidity decreases, MC decreases, and the wood shrinks. This relationship is referred to as Equilibrium Moisture Content (EMC), and can be accurately predicted.
Anatomy of a Clarinet Crack Repair
Avoiding Cracking In Wooden Clarinets
Finally, we'll call it a day by listening to the original Canon by Pachelbel (not Taco Bell, guys, let's get that PERFECTLY understood), and then by watching the next guy gripe about it.