Frozen pipes!
With cold weather here, remember the pipes. Open those cabinet doors to allow some warm air around the plumbing; especially at night. If you have plumbing areas that have frozen in the past, pay special attention to these areas now. Allowing the plumbing to drip slowly can help. If you have enclosed glass showers, keep the door open so the heat can get in there. The safe use of space heaters in bathrooms, kitchens and laundry areas help greatly.
If the pipe is already frozen: turn up the heat in the house, use space heaters if necessary. Keep the air circulating. Make sure you know where the water shut off is and you can quickly get to it if a pipe breaks.
If your garden hose is still connected, it has likely frozen and busted the line. Freeze proof spigots usually won't leak until you turn them on in the spring. Be ware!