Digital TV platform Freeview says that people around the UK are experiencing reception problems because of high-pressure weather conditions.
Freeview’s free-to-air channels include those from the BBC, Channel 4, Channel 5 and ITV.
The website Downdetector has nearly 5,000 comments from viewers reporting that they can’t access channels at all, or that the picture is distorting.
Freeview says those affected should not re-tune their TV sets or boxes.
“At the moment, it looks as though these conditions may continue throughout the week,” Freeview said in a statement.
A spokeswoman told the BBC it was unclear how many people were likely to be affected, but the high pressure was over Wales, south-west England, south-east England, East Anglia, parts of the Midlands and Yorkshire.
She suggested using internet-based services like the BBC iPlayer, internet-connected TVs or the Freeview app as an alternative.
However some Samsung devices have been unable to work with the BBC iPlayer since 6 December.
“BBC iPlayer is no longer available on some Samsung Blu-ray, DVD player and set-top box devices, as they are unable to support the technical requirements needed to keep BBC iPlayer going,” the BBC said on its site, which lists the models affected.
It’s not the first time weather conditions have caused problems for Freeview – in November 2017 some viewers complained that they missed the final of The Great British Bake Off as a result.
Analysis: Nikki Berry, BBC Weather forecaster
There is currently a large area of high pressure across the southern half of the UK and extending across much of Europe. Pressure readings in the London area were 1030mb this morning which is high, but not unusually so.
However, it isn’t the high pressure itself which causes interference with TV signals. It’s the presence of what is known as an atmospheric temperature inversion. A temperature inversion is when a layer of warm air overlays cooler air at the surface. Temperature usually decreases with height above the earth’s surface, but when there is an area of high pressure, the air aloft sinks down towards the earth’s surface and it warms up as it does so.
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This creates a sharp thermal contrast in the atmosphere which TV and radio waves see as a physical boundary. There are many TV and radio waves travelling through the lower atmosphere and in such atmospheric conditions, these waves can be refracted or bounce off the inversion overhead and this enables them to travel much further than they would otherwise be able to.
In this way, the usually strong Freeview signals can experience significant interference with other, normally distant, signals from other sources.
Will these conditions persist? Inversions tend to break up. The current high pressure over the UK is likely to slowly weaken over the next couple of days.
Inversions may still form overnight for the next couple of nights, particularly in the south of the UK, but they are not expected to be as sharp or close to the ground and so should have less of an effect on Freeview signals.