Weather conditions can degrade a television signal, this degradation manifests itself differently on digital as it did on analogue. We could see the signal problems on analogue televisions resulting in ghosting, snowy picture, lines on the screen, and various forms of patterning in the background spoiling our viewing.
With digital, its different, a poor signal here causes the picture to break up into small squares known as 'Pixelation', freezing or even disappear altogether.
Due to the methods used in delivering a digital signal, it makes it immune to effects like ghosting.
Under 'high pressure' weather conditions and given the fact that digital signals are low until digital switchover is achieved, pixelation or loss of signal is possible in some circumstances.
Apart from the obvious problems caused by poor fitting or old rusted aerial systems in high winds, the movement can cause pixelation or monmontary loss of signals.
The movement in trees close by can also effect the signal, especially if the leaves are wet.
Rain or Fog:
Heavy rain or fog will cause a reduction in signal levels, again causing breakup or loss of picture. If after the rain clears problems still persist, its possible water ingress in the coax cable has occurred, the only remedy here is replacement of the cable. If this is left, then corrosion or rust can be seen on the aerial plug indoors.
What ever the weather conditions, the effects on a digital signal are the same i.e. breakup, freezing or loss of picture altogether.