With the temperatures dropping below freezing it’s important to protect exposed pipes from freezing and rupturing. One simple method to keep the water inside the pipe from freezing is to leave a faucet trickling overnight from the faucet located highest in the house. The trickle should be a steady stream, about the size of the lead in a pencil.
If your exposed pipes are not wrapped and insulated you should talk to your landlord about having it done. The insulation does deteriorate over the period of a couple of years so your landlord may not be aware that the pipes have become exposed.
It is also a good idea to locate the main water shut-off valve. If you need help locating the valve please contact your landlord.