The age old question, "should I warm up my car before driving it when it's cold outside?" The answer used to be yes, but with newer vehicles that's now not necessary. Most experts say you only need to let the engine run for about 30 seconds. That'll give it enough time to get the oil circulated, which isn't a big issue in today's vehicles.
The only time you should do an extended warm-up is when you're having trouble scraping snow and ice off of the windows before they're defrosted.