cold air sinks warm air rises. depending on terrain and a natural breeze it will b diff. calm wind there wont be much swirlling going on unless it goes from 35 to 60 digrees in a couple minutes, which doesnt happen. thermals happen every morning and night with the sun. in steep forested terrain ull actualy feel it. good luck man.
Well said ivorytip, you can actually play the thermals like that to your advantage. Of course, things can happen and wind will swirl but the you can add this knowledge to your hunting arsenal, they are that dependable.