Did you ever get winded by a deer when you were sure the breeze, if any, was in your favor? Or maybe a deer started blowing at you long before it should have been able to know you were there?
It could be you were a victim of thermals. Thermals are air currents caused by the heating or cooling of the earth's surface. As the ground warms in the morning, air will rise, carrying your scent with it. If you expect your deer to approach from uphill, that could be trouble. In the evenings, as the ground cools, thermals will flow downhill.
You might not feel thermals, but be certain that your scent is riding on these invisible hunt-killers. As a general rule (and always keeping prevailing wind in mind), set up your stands above deer trails in the morning and below the trails in the evening to beat thermals.
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