Sinking Thermals: The Most Consistent Wind Direction


Hunters have complained about thermals for decades, but once they are understood, they can be a friend rather than an enemy.  Most hunters can imagine air and scent molecules being moved by wind because we've seen how smoke rising from a fire is affected by wind. The heat from a fire creates rising thermal currents, just like the heat from the sun makes air molecules rise during the day. As air cools in late afternoon on a calm day (and on the calm side of a hill or ridge on a breezy day),  the humidity percentage increases, making the air heavier, pushing it towards the ground. During calm conditions, this heavier air will flow downhill like water flowing over your boots toward the sea. This downward thermal wind direction will persist all night and well into the next morning if a stronger wind doesn't overcome it. Cloudy, humid days can present all-day sinking thermals if the winds are calm. These conditions are optimal for mature buck movement. Under these conditions your scent molecules will travel to the ground whether you are up in a tree or in a pit blind. From a tree stand your scent will travel through a vertical column from your head's height all of the way to the ground, dispersing to contaminate a large area.  Because the top of your head is only three feet from the ground when in a pit blind, your falling scent is already below a traveling deer's nose. A deer just ten feet downhill (downwind) of your pit blind will be unable to smell you if it doesn't have its nose on the ground. Deer uphill (upwind) will also be unable to smell you. We should try to always be downwind from our quarry, and sinking thermals are the most common and consistent wind direction we experience while hunting. Remember to set up below the deer's nose level when the thermals are sinking, or as I like to say "When the thermals are down, you should be on the ground." The early morning and late afternoon periods of calm days (and calm areas on breezy days) present the best conditions to encounter a buck on his feet during daylight hours. Take advantage of the most consistent wind direction - sinking thermals. Having a pit blind within sight of your tree stand may sound strange, but matching your hunting method to the conditions of the day can make all the difference in the outcome of your hunting season.     

Paul Keller