Adverse weather conditions have been known to affect the quality of the satellite TV signal reception. This is popularly called "rain fade". Usually, when this occurs, it is only for a short period of time. In reality, heavy rains and cloudy conditions can affect television signals enough to result in noticeable degradation of image quality.
In very severe cases, reception can be effectively disrupted. Factors that determine how often this will happen include regional yearly rainfall figure, location in the satellite footprint and height of the satellite above horizon.
While it takes very heavy rain to affect signal reception of a properly aimed and wired satellite home system, still, it can and will occur where the conditions are present.