I have a Buick La Cross 06 and the weather has dipped down in the -teens high of 9. My car when started in the mornings sounds like there is something hitting some molding- like fan shroud or something. But warm it up at an idle for 10-13 minutes and the sound goes away. I have replaced the oil and filter, checked to see if there is any thing loose but it sure sounds like it is coming from the engine. What in the world could be making this sound and is it serious? Is there an oil pump?
Without hearing it, the noise is hard to diagnose however, it could be your power steering. Does the noise get louder when you turn the wheel. When it is cold it is normal to have some more noises. GM does offer a different power steering fluid for colder temperatures.