For pipes to freeze inside of a house or protected area the temperature in the house or area has to drop to 20 F or below in order for the pipes to freeze and bust.
If the pipes are exposed outside or in windy conditions then the pipes can freeze at 35 F or below.
You should wrap any exposed water pipes in heat tape and insulation and protect them from the wind to keep them from freezing.
Leave faucets dripping on really frigid days or nights to prevent the pipes from freezing and busting which can cause major damage to your home and an expensive repair bill.