Changing oil on e90

Hi,



This is probably a really dumb question but its going to be my first time changing the oil of my car by myself. I've read on several guides that i should let my engine run for at least 2-3 min. before i change the oil. Why is that so? I know its so i can warm the oil a little bit, but why do i need to warm the oil why can i change it while the engines and oil is cold or room temperature?



Thanks!!!!