[Studio25]

Does it happen only during bad weather?

The old "snow" problem isn't present on modern TVs. It was caused by RF interference from electrical devices adding to the received signal from Winter Hill. Because your TV was analogue, it didn't interpret or decode what it was receiving, it just displayed the signal it was receiving, interference and all.

These days, it's a digital signal, which is either on or off. You might occasionally get a corrupted frame, which results in the moving part of the programme looking like it's gone through a 1970s Top Of The Pips pixellation filter, but you don't tend to get random "snow".

If the reception is bad enough for long enough, there's not enough salvageable data and so your TV may just go blank and silent. It depends on the software, mine freezes with a still image.