Actuator, or the dish motor arm, can freeze. The actuator is what is connected to the motor that moves your satellite dish. If it freezes, your dish will not move from its present location. This will cause some channels to be weak or have low signal quality. If the frequency shift is severe enough, then you will not be able to receive any channels on your system.
Winter is the roughest time of the year in some parts of the country.
And it can be especially rough on your satellite system. Polarity Servo Motors can work slowly or stop completely, due to the cold weather. This will cause the loss of either odd or even channels. Build-ups of ice and snow can warp or bend a satellite dish. A warped satellite dish can result in low signal quality or complete signal loss.