Routers run warm, and that's normal. They work twenty-four hours a day, and all the power they draw eventually becomes heat, there's nowhere else for it to go.
The problem isn't the heat but heat with no way out. And the symptoms rarely look like a heat problem; they disguise themselves as slow internet.
Recognising the symptoms
What distinguishes a heat problem from a network problem is that the pattern follows the clock, not what you're doing.
- Slow during the day, normal at night. This is the strongest clue. Network faults don't care about room temperature.
- Fine after being switched off briefly, worse after a few hours. A cool device behaves normally, then degrades as it heats up.
- Restarts by itself with no power cut. Some routers reboot deliberately once they pass a temperature threshold.
- Wireless range shrinks though nothing was moved. A hot radio reduces its own output.
- The 5 GHz band drops before 2.4 GHz. That section typically runs hottest, the difference is explained in the guide to 2.4, 5 and 6 GHz.
If the pattern instead follows busy hours, evenings, when neighbours are also online, the cause is probably not heat but what's covered in the guide to internet slowing at certain hours.
A simple test that separates the two. When symptoms appear, switch the router off for ten minutes, then back on. If it clearly improves and degrades again after an hour or two, it's heat. If it improves only momentarily or not at all, look elsewhere.
How hot is still acceptable
Routers don't display their temperature, and most people have no way to measure it. Fortunately a hand works well enough as a rough gauge.
| What it feels like | Roughly | Verdict |
|---|---|---|
| Warm, comfortable to hold indefinitely | About 35–45 °C | Normal |
| Hot, hand tolerates a few seconds | About 50–60 °C | Upper limit, worth fixing |
| Hand pulls away reflexively | Above 65 °C | Too hot |
Some routers show temperature in their settings panel, usually on the status or system information page. Where available, that figure is more trustworthy than a hand, and useful for comparing before and after a fix.
The most common causes
Nearly every overheating case comes from one of five things, listed roughly in order of how often they occur.
Stacked or covered
Sat under a set-top box, inside a drawer, behind books, or draped with cloth. This is the most frequent cause and the easiest to correct.
Vents clogged with dust
The grilles on the sides and underside close up slowly over years. Nothing announces it, and nobody checks.
Standing on a heat-trapping surface
Glass, metal, and thick wood hold in heat that should escape through the base. Some routers rely on their underside as the main exit.
In direct sunlight
A router near a window can gain tens of degrees during the day without doing anything at all.
An ageing power adapter
An adapter far hotter than it used to be, or a swollen casing, is a problem in itself, and it both warms the router and feeds it unstable power.
Cooling steps, starting with the free ones
The order deliberately begins with what costs nothing, because most cases resolve within the first two.
Give it room
Ten centimetres clear on every side, and nothing on top. It sounds trivial, but it fixes more cases than every other step combined.
While you're moving it, consider a spot that also improves coverage, both want the same thing, somewhere open and slightly elevated. The considerations are in the guide to router placement.
Clear the vents
Unplug it first. A dry brush or low-pressure air on the side and base grilles is enough. Don't spray any liquid into the openings.
Every three to six months is reasonable, more often with pets or in a dusty room. The related upkeep is covered in the guide to making a router last.
Change how it stands
A router designed to stand upright shouldn't be laid flat, and vice versa. The wrong orientation blocks the airflow path its design depends on.
If it sits on glass or metal, a thin wooden mat or a slotted stand is enough to improve matters. What counts is that the underside isn't pressed flat.
Remove unnecessary load
Features left on but unused still draw power and produce heat. The most common: a 6 GHz band in a home with no devices that use it, and transmit power set to maximum in a small home.
Lowering transmit power sounds counterintuitive, but in a small home it often improves things, the explanation is in the guide to boosting Wi-Fi signal properly.
Only then, a fan
If all four steps are done and it's still hot, a small USB fan aimed at the grilles does help. Two caveats: don't power it from the router's own USB port, and make sure it isn't blowing dust inward.
Don't drill the casing. This idea resurfaces periodically on forums. Besides voiding the warranty, extra holes change an airflow path that was designed deliberately and often make things worse, air enters through the new opening and stops passing over the parts that needed cooling.
When it turns out not to be heat
If every step is done and the symptoms persist, the cause is probably elsewhere. Some things that look similar:
- Connections dropping periodically more often originate with the provider or the cabling, see the guide to dropping Wi-Fi.
- Full signal but slow has its own causes unrelated to temperature, see the guide to full signal but slow internet.
- Slowing down in rain points to a physical connection outside the house, see the guide to internet problems in rain.
- Unstable mains power produces symptoms much like heat-triggered restarts, see the guide to UPS for routers.
What the indicator lights show when symptoms appear often narrows the search quickly, see the guide to router indicator lights.
When heat means it's time to replace
Heat that placement, dust, and room conditions can't explain usually means the internal components have aged, the power supply section in particular.
Fairly conclusive signs: a swollen casing, a faint burnt smell, an adapter far hotter than it used to be, or a device that needs weekly restarts when it never used to. When three of those appear together, repair is rarely worth it.
The replacement decision is covered in the guide to when a router should be replaced, and the choosing in the guide to choosing a router.
Closing notes
A warm router is normal; a router whose heat is trapped is not. The difference shows in the pattern, heat problems follow the clock and the room, not what you happen to be doing.
The first two steps resolve most cases and cost nothing: give it space, then clear the vents. An added fan is the fifth step, not the first.
Frequently asked questions
How hot can a router reasonably get?
A casing that's warm but comfortable to hold for a few seconds is normal. If your hand pulls away reflexively within a second or two, it's past the temperature that's healthy to sustain for years.
Why does the router restart itself during the day?
A pattern that follows the clock, restarts in the afternoon, fine at night, almost always points to heat rather than a network fault. Some routers deliberately reboot once temperature crosses a threshold, to protect their components.
Can I add a fan to a router?
You can, and on a genuinely cramped router it helps. But most cases resolve earlier by moving the device somewhere open and clearing its vents, without adding anything.
