From my experience, setting the boild pot outside in the cold doesnt chill it very quickly at all.
Example: My first batch was brewed on one of the coldest nights of the year so far (about -10F, windchill around -30) I decided to pack the boil kettle in the snowbank and leave it to cool. Well apparently I didnt pay much attention in science class, and nearly 3 hours later my beer was finally at a pitcheable temp.
I found out that the intense heat of the kettle actually melted the snow around it enough to create an air gap between the snow bank and the kettle. This served as a nice insulator keeping the heat in. I assume this is closely related to building an igloo.
Lesson learned. Until I decide to invest in an immersion chiller, I will be utilizing the ice bath from now on.
One question: Does anyone use a frozen water bottle (such as a 2 liter pop bottle) and actually submerge it in the wort? Obviously it would have to be sanitized before hand. But I have heard of this method being used before, just wondering it is advantageous or not?