I was once told by an old boy who used to work in the labs developing lubricants that you should never leave the car idling first thing in the morning (apart from the first 10 seconds of course to make sure the oil pressure is up) because the quickest way to get the oil warm was to drive the car, obviously don't nail from the start but drive of steady and you will be OK. Modern technology in automotive oils allows this in quite extreme weathers so I wouldn't worry about it.