Turn on your home heating, open any cabinet doors and keep the door to the bathroom open. If the shower is in a stall with a door of its own, open the door to increase the amount of airflow reaching the wall with the shower pipes.
Turn on the shower. Although nothing will come out initially, of course, as the water melts, opening the shower valve allows it to drip out instead of building up in the pipe.
Set a hair dryer on low and run it along any exposed portions of the pipe, such as the part between the wall and the showerhead. The Lincoln Water System in Lincoln, Nebraska, suggests using a heat gun set on low, but it cautions that both heat guns and hair dryers can set wall material and wood on fire if you aren’t careful.
Run wet, warm towels along exposed piping.