What this usually means
A dimmer that is mildly warm can be normal, because dimmers dissipate heat. A switch that is hot, newly warm, discoloured, buzzing or smells is not. Stop using the circuit and have it evaluated, because heat at a switch usually means a connection or the device itself is failing.
The common causes
An electrician works through 5 conditions that all produce is my light switch or dimmer warm. They are listed so you can describe what you are seeing accurately — not so you can decide which one applies, because several of them look identical from outside the equipment.
- Normal dimmer dissipation — Dimmers produce heat by design, more so in a multi-gang box or with a high load.
- Loose termination — A loose conductor at the switch heating under load.
- Load above the device rating — A dimmer or switch controlling more load than it is rated for.
- Incompatible lamps — Some LED lamps and dimmers interact badly, causing heat, flicker or buzzing.
- Failing device — Internal contacts breaking down.
What to note before you call
For this symptom specifically, 4 observations do most of the work. All of them can be noted without opening any electrical equipment. Having them ready turns a vague call into a productive one and shortens the diagnostic visit.
- Whether it is warm or genuinely hot to touch
- Whether it is a dimmer or a plain switch
- Any discolouration, buzzing or smell
- What lamps are fitted and whether they changed recently
What happens next
An electrician tests the circuit, isolates the cause and explains what the repair involves before doing it. Where this points at outlet, switch and gfci repair, that page covers what the work usually includes and what changes the scope.