as said above but instead of just ice a lot of salt and water to get even colder. if you want even more extreme replace all that with just dry ice in the bucket around the base. becareful though you base can blow up so if you have an acrylic base use it. if you go with dry ice please do it with a window open or outside because you will get more co2 than normal in the air so its a little iffy.
also beware that there is a point where smoke is too cold to where the point it almost "burns" your lungs.