Impact of humidity on tuning

[raduray]

I keep my guitar on it's stand during warm weather here in Massachusetts. I find that when it's humid I need to adjust the tuning down, and when the weather's dry, I need to adjust up. Can someone explain the mechanics of what causes this?

[Pnewsom]

The belly of the guitar's top expands and rises with higher humidity which increases the tension on the strings slightly, so you have to tune down a little. The reverse is true when the humidity goes back down.

The action on the guitar also raises a bit with the increase in humidity making it a little more difficult to play. Some folks have a lower second saddle made to compensate for this during the summer and switch back in the fall.

It takes some time for this effect to take place, and keeping the guitar stored in a quality hard shell case except when you play it can slow this effect down considerably.

[ManyMartinMan]

Originally Posted by raduray

I keep my guitar on it's stand during warm weather here in Massachusetts. I find that when it's humid I need to adjust the tuning down, and when the weather's dry, I need to adjust up. Can someone explain the mechanics of what causes this?

The guitar swells and contracts. If you eat too much (swell) you have to let your belt out. If you don't eat for a week, you'll have to tighten the belt. Simple mechanics -