You set the parking brake overnight in freezing weather, and in the morning it will not release - the car will not budge or you hear the rear brakes dragging. A frozen parking brake is a classic cold-weather problem. Here is why it happens and how to deal with it safely.
Why it freezes
The parking brake holds the rear brakes mechanically through a cable - see how the parking brake works. In winter, moisture inside the cable housing or between the shoes/pads and the drum or rotor freezes solid, locking everything in place. Slush, road salt, and a warm brake that melts snow then refreezes all make it worse.
How to free it safely
Do not force the car forward hard - you can snap a cable. Instead, try releasing and re-applying the brake several times to break the ice, gently rocking the car in drive and reverse, or warming the rear brake area (a garage, or pouring warm - not boiling - water on the frozen spot). Patience and gentle rocking free most frozen brakes without damage - similar in spirit to a stuck parking brake.
Avoiding it in winter
The simplest prevention: in very cold, wet conditions, many drivers skip the parking brake and instead leave the car in Park (automatic) or in gear (manual), chocking a wheel on a hill if needed. Drying the brakes with a few gentle stops before parking, and keeping cables lubricated, also helps. If you must use it, know how to free it.
When it points to a deeper issue
A brake that freezes easily every time, or a cable that stays stiff, may have a corroded or failing cable that needs service - and worn rear shoes/pads should be replaced. Keep the rear brakes healthy with quality pads and fresh hardware.