Leaving it outside will cool it down, tho very slowly, and its not really worth doing.
Instead, you would be much better off to fill your sink/bathtub up with cold water and ice and let your covered pot cool in the water. Water is much better at transferring heat than air/snow. However, if you still want to cool the wort outside, find a big tub, fill it with cold water, then put your covered pot in the cold water and move the whole thing outside or into a snowbank. Works great.