Seals shrink when it's really cold; every mechanic I know in the LA area loves winter because that's when they get all the cars coming in with leaks. It could be any number of areas; if it's near the rear of the engine it could be head gasket seals, if its near the front you have a range of choices. The two I read about most often are the bottom of the coolant tank or the lower radiator hose where it meets the radiator. There are a few scarier options but they would be consistent, not just with the cold.
Life is too short for bad tone or crappy cars.