Virgin Media has told its customers to keep wi-fi routers out of direct sunlight in case they overheat.
The warning was contained in a recently published page offering "top tips for a strong, reliable connection this summer".
Overheating is a problem to which many electronic devices can be prone.
If the router becomes too hot, it may "slow down your connection or even grind to a halt altogether", the company warns.
But there was "no widespread issue" of hubs overheating during the current England heatwave, a Virgin Media representative told BBC News.
And the company said it tested devices to ensure they worked in a range of temperatures.