Understanding Thermals and How to Hunt Them

Understanding Thermals and How to Hunt Them

By David Holder

It’s one of those mornings that as a bowhunter we all dream about. It’s the last week of October and the first cool front has moved in over the last 24 hours. This shift takes daytime highs from the mid 70’s to the mid 50’s. So, it’s not surprising at all, since this morning is dead calm and 36 degrees that you could hear this buck walking in the leaves long before you ever saw him. Your heart is starting to pound. Not only does this appear to be the biggest buck you’ve seen while hunting, but also because he is on a straight-line path to your location. You’re ready! Your bow in hand, your arrow nocked, and you previously ranged several trees in the area from where he is coming. All he must do now is close the distance.

The buck is sixty yards and closing the distance, heading to fifty yards, now forty yards. You’re now thinking this is going to happen for sure. But then the inevitable happens. The buck, who just seconds ago was completely oblivious to anything and everything, has now locked-up staring in your direction. Your heart starts to sink as you know he can’t see you; you haven’t made even the softest of sounds. As far as you can tell, the wind isn’t blowing in any direction. As all this runs through your head, the buck suddenly blows sharply, turns, and bounds back in the direction from which he came. You hang your bow up, sit down, and try to figure out what just happened.

Scent Travels! Even When There is No “Wind”
What just happened, is the wind or more importantly the lack of wind just got you busted. You see when there is no wind, your scent will follow the thermals. If it’s early enough in the morning and the temps haven’t started to rise yet, those thermals will carry your scent to the bottom of your tree… sort of like a “scent bomb”.

Just in case you aren’t familiar with thermal winds, here is a quick description. When temperatures change for any reason at all, warmer air, being less dense, will rise. Cooler air, being heavier, will sink, which explains what happened in the situation above. The cooler air, and the fact that there wasn’t any wind, meant the thermal columns were carrying any human scent downwards from the stand to the ground. Once the scent made it to the ground, without any wind, the scent basically builds up and spreads out sort of like a mushroom affect.

Now, using that same scenario, but saying the deer doesn’t approach for another hour when the sun has come up and the ground temperatures have begun to rise, you could have the exact opposite outcome. Now, knowing this about the wind, how do we go about using its effects to our benefit? Let’s look at a few things we should consider.

Evaluate Wind Direction
First and foremost, before we look at thermals, we must understand basic wind directions before heading out to hunt. Check the wind direction and speed using a handheld wind checker or by observing the movement of vegetation. Knowing the wind direction is crucial as it helps you position yourself or your stand downwind of un-expecting quarry. It’s good to make it a habit to check the wind periodically through each and every hunt as several contributing factors can change wind direction and drastically affect the thermal columns in your area.

Some of the elements that can change the thermal column are simple, but if you’re not paying attention they can be overlooked. Since temperature variations are the biggest culprit to thermal winds, it would make sense that if you notice a strong cool front move in, say 20 degrees or more, in a short amount of time, this alone could drive scent downward. You will notice the opposite in temperature, you can expect the thermal column to react accordingly by doing the opposite as well. Keep in mind sometimes it may be as simple as cloud cover that can change the temperature enough to change the wind direction.

So, let’s talk a little bit about wind in general. After all, when it comes to big game hunting, the wind has saved more animals than any of us would care to admit. If you don’t understand the wind, it can be more than frustrating. Even if you do understand the wind, sometimes it just doesn’t blow our way. Trust me, the animals we chase have seen both sides of the wind game as well. However, don’t be surprised when you find your dream buck spending most of his time in a place where the winds work in his favor more often than not. He may have found the spot randomly, but might understand it’s in his best interest to return there time and time again. This pattern is not coincidental it’s purposeful. Remember, for him his life depends on it. Yes, there are places where certain animals are un-killable, don’t waste your time hoping for a miracle, or worse yet don’t buy into some of the other gimmicks on the market. No matter how much hype you hear from manufacturers claiming their product will eliminate any detection, don’t believe them! Always, I repeat always hunt the wind. Even the best scent control products may only have a minimal effect. Now I’m not saying don’t actively try to control your scent. In fact, do the exact opposite. Do everything you can to control your scent, but still only hunt from a downwind position.

Study Nearby Topography
Temperature may have the greatest influence on thermals, but topography can also play a huge role as well. Things such as steep draws, rock formations, creeks and river bottoms are permanent parts of the landscape that will cause temperatures to stay cooler. These areas can actually create their own wind directions as long as actual wind velocity is not so great that it takes over. Understanding how to utilize these types of locations to your advantage can be a game changer in your arsenal of hunting tips.

Choose stand locations wisely meaning, select stand locations that allow you to take advantage of wind patterns. Look for natural features like ridges, valleys, or terrain contours that can create thermal updrafts or downdrafts. These updrafts/downdrafts can help to carry your scent away from the game, making it harder for them to detect you. If at all possible, enter your stand from downwind. While moving towards your stand, ensure that the wind is blowing from the stand towards you. Entering your stand in this fashion will allow you to remain undetected as your scent is carried away from the game by the wind. Sometimes paying attention to the smallest of details can generate the largest of rewards.

Thermals Summarized
So, let’s recap what we have learned so that we can go out and use our newfound knowledge to get as close to our quarry as possible. Number one: you can’t eliminate your scent, but you can buy yourself a few seconds with good and proper scent control of you and your equipment. Number two: the only way to stay undetected is keep the wind in your favor. The only way to do that is to understand the wind (check it often throughout the hunt as it doesn’t take much to change the wind).

Number three: thermal columns can play a huge role in our hunts. We must remember to pay attention to every little detail (warmer air rises, cooler air sinks). Number four: thermal columns won’t be the determining factor if wind velocity is high enough to supersede the thermal column. Last but not least, if you pay attention to the little things, you may just end up with your next buck closer than you ever expected, while you, remain undetected.