Why do guitars get out-of-tune on rainy days?

Answer 1

The wood expands with the humidity and the strings don't

Answer 2

Remember, wood is still very much active in terms of movement.

As room conditions change, so does the wood.

The wood in its settled state has a very slight dip in it, rather like a bow. A subtle c-shape with strings from top to bottom. This can be adjusted by a luthier using the truss rod (a metal rod inside the neck designed to adjust the curvature).

As the room humidity increases, the neck of the guitar puts up less fight against the strain of the strings. Remember the strings are constantly fighting the wood and are under a lot of tension.

As the wood gives in and bends inwards very very slightly, the slack is created on the strings, making them go out of tune. The opposite happens when the humidity decreases.

This is no big deal, however you should considering keeping the guitar on a stand in the same room all year. This can insure a free circulation of air, and also allow the wood to move freely with the conditions.

Note that heat / cold in excess can be a bad thing for a guitar. What type of fretboard do you have? You can spot and rectify the early sides of a dry-fingerboard.

Chris.

Answer 3

I've never made that connection but assuming its true I guess the wood and pegs get more moisture in them causing a change. Perhaps you should Write a song about it. A-g-d with the opening line "WHy do guitars get out of tune on........

Answer 4

Not to add a question to your question, but do you find the strings go flatter (looser) or sharper (tighter) ?

For some reason mine always have to be tuned down after I've been playing for weeks on the guitar. Makes no sense to me, but the strings seem to tighten with use. Crazy, isn't it?

Answer 5

Humidity causes changes in wood and strings (this is via my ex, who plays a guitar)