The Insurance Information Institute (III) says you should keep your home warm to a comfortable temperature of at least 65 degrees. This is because the pipes are located inside the walls and the temperature there is much colder than in the rest of the house. Any temperature lower than 65 degrees, according to III, may not prevent a freeze from occurring within those walls. As a general rule, outdoor temperatures must drop to at least 20 degrees or lower for pipes to freeze.
In Nordic climates, where temperatures regularly drop below freezing, modern homes tend to be well insulated and water pipes are located in the interior parts of the house for greater protection. In old houses, this is not always the case. In southern climates, severe frosts can be more problematic because the houses there aren't built to withstand cold temperatures. Many people welcome the cold, cool winter weather, but no one likes the pipe-related headaches that can come with falling temperatures.