Run your thumb along the treble side of the neck some February evening. If you feel sharp metal at the fret ends, that is not a setup problem. That is the fretboard shrinking because your heating system turned the room into a desert weeks ago, and nothing told you until the wood moved.
What winter actually does to a guitar
Forced-air heat works by pulling in cold outdoor air and warming it up, and warm air that started out cold is extremely dry. Indoor humidity can fall from 50 percent to under 30 in less than a week of hard frost. The wood responds on its own schedule: the top shrinks across the grain, the fretboard contracts while the metal frets stay the same length, and suddenly fret ends are poking out and slicing your hand on every position shift. Action drops, buzz shows up on the first five frets, and most players blame the truss rod. The truss rod is innocent. The room did it.
Wall-hung guitars feel it first
A guitar in a case breathes slowly, and a decent case humidifier can carry it through most of the winter untouched. A guitar on the wall is in full contact with room air around the clock. That is the trade you make for having it out where you can see it and grab it, and it is a fine trade as long as you can watch the air it hangs in. What does not work is trusting a sensor in the hallway to describe the air at the hang point.
A $40 humidifier beats a $300 fret dress. Every single winter.
Early warning signs
- Sharp fret ends when you slide thumb-side
- Low action with buzz near the nut
- Hairline cracks at pickguard or soundhole
- Bridge or top looking visually flat/sunken
- RH below 40% at the headstock for more than a few days
Wall-hung rule: if you would not sleep in that air without a humidifier, your guitar should not either.
Winter playbook
- Run a room humidifier targeting 45–50% RH where the guitar hangs.
- Keep the instrument away from direct heat vents and radiators.
- Check RH daily when outdoor temps stay below freezing. The free room check shows where your air sits this week.
- Put the reading where you will actually see it. HygroMount shows RH and temperature right on the mount, with no app and nothing to pair.