Understanding Thermals in Whitetail Country

Thermals occur when the ambient temperature starts to change, typically in the morning and the evening. In the morning, if the sun is out and warming up the ground, the air will rise (hot air is less dense than cold air). In the evening as the sun dips behind the trees, the higher air starts to cool and sink. During both events, the thermal carries your scent.

These shifting air currents have implications for hunters. Anyone with a few elk seasons under their belt knows that elk use thermals to their advantage every day. Well, whitetails do too. They live off of their noses, and if you think they don’t know the conditions in which rising air will tell them of dangers below, or when sinking air will clue them into potential danger above, you’re fooling yourself. Deer, especially mature bucks, spend their entire lives in roughly one square mile, and they know where, and during what conditions, the wind favors specific routes and bed choices in their home range.

They use thermals to survive, and this means that you can use them and their daily likelihood to your advantage, or at the very least, avoid them working to your detriment. This might not seem like much of a concern if you live in a plains state, but remember that an elevation change of 50 or 100 feet, like those found along rivers that course through mostly flat areas of the country, can experience thermals. And those are the places whitetails live.

Think about your stand sites and how thermals coming into play when you set them up. Before a sit, check the hourly forecasted temperatures. If they aren’t going to change more than a few degrees throughout the day, you won’t have to worry. If they are going to rise or drop several degrees after first light or just before the closing bell, thermals will occur.

If you’re on a ridgetop for an evening sit and have a bedding area or maybe a destination food source below you when this happens, you might be in trouble. The cooling air is going to pull your scent down, and while it won’t be as obvious as a breeze coming out of the west that you can feel and hear, it’s still a factor—particularly for bowhunters who are playing a close-range game. Peak up-and down-drafts coincide with the times of day when the best deer movement occurs.

You might not have to deal with thermals for 85% of your sit, but during the first and last parts, you will. You might also have to deal wind eddies, which have been saving elk and whitetails for as long as we’ve been hunting them. Eddies (swirling winds) are the reason that many seasoned hunters won’t sit in bottoms or steep valleys when whitetail hunting.

Having grown up in the bluff country along the Mississippi River, I can attest to the very real impacts and importance of thermals, but also know that they vary spot-by-spot and day-by-day. Knowledge of thermals and wind eddies can help you sketch out vague plans, but theory will only get you so far. Ultimately, if you want to figure out how air movement impacts a particular hunting area, you have to spend time there. If you hang a stand in a tight valley hoping to catch bucks crossing low, use a wind-indicator or better yet, grab a milkweed pod and watch how the seeds travel throughout your sit. Sometimes the thermals and swirling winds won’t affect your odds, other times they’ll shut down a spot.

The best way to learn is to hang a stand, keep checking the wind, and see how it goes. You’ll want to factor the potential for thermals in, just like you would with prevailing wind direction, but you’ll also want to see how that actually plays out in a spot. You might bust some deer, but you might also find an ‘unhuntable’ spot to be more viable than you thought.

Feature image via Captured Creative.