This is usually caused by a loose or improper coax cable fitting at your dish LNB or ground block. Check those if you can easily reach them. A coax cable fitting with a center pin that's cut too short shrink enough in very cold weather to cause this sort of problem, as can a loose coax connector. Rarely, the LNB itself may be temperature sensitive.
If you can't easily reach the dish to check those coax connectors, it's best to call DirecTV for a service visit.