SATCOM in the Ku- and Ka- bands, as well as EHF systems are adversely affected by rain (the higher the frequency, the greater the effect) because one of the factors that affects availability in a satellites is rain. Higher frequencies in Ka-band (30/20 GHz), rain can have a very large effect that simply cannot be overcome at the usual levels of availability.
Rain reduces the quality of signals by interfering with the signals thereby, reducing their strength and quality.
Therefore Rain can not only degrade a satellite's signal, it can also cause a complete outage of the satellite's.
