The complete guide to mountain thermal wind

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Video how do thermals work in the mountains

Elk hunting and it’s relation to thermals. Know it, or you will know failure.

Whether your target is an elk or a mule deer, thermals will be a factor in the west. Many times, thermals can be the difference between fresh tenderloin or cold tag soup. Practice shot placement. Learn how to call. Buy great gear. However, understanding mountain thermals is just as, if not more, important.

Thermals have always existed. They have been known to Western hunters since ancient times (clearly, I am talking about Native American hunters and I know how old the United States is). Now, in a world more connected, the term thermals has stirred seemingly more questions than answers. Stick with me, once you finish this article you will have everything you need to know about thermals as they relate to hunting in the mountains.

Why you need to understand thermals

Look closely at the above picture. I know it’s grainy, I took it with an old iPhone a few years ago. Notice how the elk are feeding at the base of a mountain. To set the stage, it’s dawn and late August.

Why are the elk here?

Elk live by thermals. They move, bed, and feed with diurnal thermal changes in the mountains. In this case, the thermals are moving downhill. The elk are strategically set up to smell anything approaching from the mountain, and see anything approaching from the large meadow. This is a key factor to their keen survival habits. Before the thermals switch, these elk will move up the mountain using the downward thermals to safely navigate their ascend to their bedding area.

As an archery hunter, this particular scenario would be an impossible position. You will not call them across the meadow, and it would be nearly impossible to stalk from the mountain. Understanding thermals will help you develop a successful strategy a little later in the day.

Wind versus thermals

Wind and thermals are different. Kind of. I like to think of wind as a macro-thermal, while mountain thermals are micro level.

Wind is, in the simplest explanation, a result of the sun unevenly heating the earth. Variations in temperature create pressure imbalances which creates wind. Cool air is heavier than warm air. This is why heat rises. As warmer air rises, cool air swoops in to replace the warmer air that is rising. On a very basic level, this is what wind is.

Think of your freezer. When you open the freezer door you get a blast of cold that comes out in a downward motion. Cool air falls, warm air rises.

Prevailing winds that you can set your watch to are no different. At a certain point during the day, the sun has warmed up a specific area enough that the air begins to rise. As a result, it pulls cooler air that is replacing the warm air moving up and out.

Entire regions of the world are affected by wind, all of which is essentially created by temperature and pressure. It’s a macro level thermal, so to speak.

If you happen to be some natural scientist and my terminology is making you cringe, I apologize. I’m putting it into layman’s terms. Because well, I’m a layman.

What are diurnal thermals in the mountains?

Mountains have very different dynamics than other terrains. Steep elevation variations, sun exposures, and temperature swings are among the reasons why.

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With what we discussed about wind, think on a smaller, more micro scale. Cool, heavy morning air settles downward. Sometimes, the downward air movement is so minimal that it doesn’t even register to a hunter. They move down from a ridge at first light and by lunch are blaming the wolves for no game in the area. The reality is this; any game that was below you, smelled you and left.

Then, as the ground warms from sun radiation, it begins gradually warming the air. As the air warms what happens? It’s lighter than cooler air and begins to move up the slope while simultaneously pulling cooler air down. This, in the world of Western hunting, is known as swirling thermals. It is the most unstable period of air movement and it happens as the ground warms in the morning, and as it cools in the early evening.

As the sun produces more ground heat the swirling will stop. At this time, you can expect more consistent upward movement throughout the rest of the day until temperatures begin cooling in the evening.

Understanding Mountain Thermals

Basically, sun-exposed warm mountain air goes up. Cold, shaded air goes down. But, it’s not always that simple.

You must always keep in mind other factors. A storm front can totally derail normal thermal patterns. A single dark cloud can create shifts or swirling air. Dark timber can totally shift the thermals, and sometimes it won’t affect it at all.

I was once side-hilling an open face at about mid-slope. It was 10am and the thermals were predictably moving up. As I entered some dark timber, it immediately shifted to a downward thermal. As I exited the timber, it changed back to upward. However, the next copse of dark timber I entered did not change to a downward thermal. In fact, a cow moose was bedded above me about forty yards. She smelled me immediately and got up and left.

There was some kind of temperature dynamic that was taking place and it had an affect on thermals.

Moving into the photographic report, it is important to stress now that in the woods, you need easy access to your wind checkers. If they are difficult to access, you won’t use it nearly enough. I really like the Sitka Bino Harness for this because of the side pockets that are perfect for easily accessible wind checkers. There are cheaper options available, but this one is will last many seasons. Click the image if you want one for this year.

A photographic report on thermals

Okay elk slayers, now for the fun part. We are going to examine multiple photos of mountain ranges and analyze the thermal patterns. Don’t skimp on this section, study each photo and key in on the directions.

Feel free to scrutinize this data; thermals are not always as simple as up or down. Come up with your own scenarios in these images that may differ from my analysis. Ask questions, take notes, and share this information.

Image 1Thermal air movement.

During the summer, there is almost always elk hanging in the bottom of this drainage. Sometimes it’s only a cow elk, sometimes it’s several elk. I am usually camped not far from here, and I know the area well.

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It’s easy to see why. Elk have protection and visibility towards the river, and scent protection from the slopes. They also have a quick escape route, they always run up the drainage towards that sunny slope.

In this case, the shaded hillsides spend most of the morning like this due to the sun being blocked by another mountain behind me. From dawn until about 11am, thermals will essentially move down and towards the river because it takes much longer for the ground to heat up.

Image 2Basic thermal concept

Image 2 highlights a basic mountain thermal concept. Direct sunlight is warming the ground/air much faster than the shaded slope. Thus, storm fronts and other factors aside, this is going to be the predictable thermal pattern.

Most likely, later in the afternoon or early evening, the sun exposure will be opposite of this morning image. The area you currently see exposed to the sun will be shaded, and the shaded hillside will have sun. This would effectively flip both arrow directions.

Image 3Yellow arrows: dawnRed arrows: about 8:30am

Love this image. Let’s analyze the morning thermals from this ridge at two different times.

The yellow arrows signify first light/dawn. Red signify two or three hours later. Notice that sunlight does NOT necessarily mean upward thermals. At dawn or first light, the sun has not generated enough heat to impact the thermals, so they are going downward. After a few hours, they switch in the left-side arrows. The ground has warmed.

However, notice the direction on the right-side arrows. They remain in a downward thermal. This is because the sun takes longer to reach this slope due to directional face. It could be closer to noon before this thermal switches. Another possibility would be longer swirling thermals.

Exact times for thermal shifts can vary greatly from one mountain to another. Especially from state to state. Sun exposure, regional climate, elevation, daily weather, and obviously geographic region will factor thermal shift times.

In my area, you can generally expect downward thermals until close to 9am, swirling thermals for 30-60 minutes, upward thermals from 10am until about 5pm, another swirling cycle, then downward thermals to dark.

This is where I need to be careful, the above mentioned time chart is very generalized and a reference to only my local hunting regions. North Idaho could be different than Southern Arizona. The Oregon and Washington Coast will be different than the Bighorns in Wyoming. However, this rule of thumb will play out within a reasonable range of time throughout the American West.

Image 4Mountain thermals mid-day

Getting a little more in-depth in this photo. I want to provide a few points about mid-day and various seasons.

Mid-day hunting in September will have different thermal patterns than say, November. It is completely plausible to see the above thermal patterns at 1pm later in the season. Cooler fall temperatures are setting in. The directional sun exposure begins to shift. Some parts of the mountain may not have direct sun exposure all day long. With cooler fall temperatures, thermals can quite easily remain in a downward pattern from dawn to dusk.

Notice in this image the varying thermals. Crossing one drainage slope to the other side can completely shift thermals to up or down. This can happen any time of the year, not just late season hunting.

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Importantly, the up-down arrows referenced “cloud shade” can be tricky. A fast moving cloud that temporarily shades a point on the mountain will most likely not affect the thermal direction. However, a slow, lingering cloud can. Typically, what I’ve noticed is a lingering cloud will give you some swirling effects.

Just monitor the lingering clouds or the very large clouds that hide the sun for long periods of time. They can and will create thermal shifts.

Image 5Thermal variations

This image can be found on my home page, I took it during archery elk season, 2018. As a side note, there were huge cutthroats in that creek, literally visible from where I snapped this image.

Predictably, most of the arrows show an upward thermal direction throughout the drainage slopes. However, see the two lines on that North-face with opposite arrows? There were elk bedded down at about mid-slope. Sadly, all cows and they totally busted me and fled.

Once I hit that slope, there was no noticeable thermal direction. My wind checker revealed that the thermals would go up and down and seemed to changed with every step I took.

My goal this day was to stay mid-slope, moving horizontally where I was finding elk bedded. It was perhaps the most consistent thermals I have ever experienced but the heat created other factors that were difficult to overcome.

Concluding mountain thermals

Let’s say you live in Pennsylvania or Kansas and have been wildly successful hunting whitetails. You’re planning on heading West in pursuit of high mountain elk or mule deer.

Typically, hunters like this do their due diligence when it comes to strategy, gear, E-scouting, learning elk calls, and learning about elevation sickness.

It’s thermals that destroy hopes and dreams. Even amongst experienced western hunters, thermals and a lack of understanding basic thermal dynamics will quickly and quietly send your targets packing. Sometimes miles away.

If you have stuck with me throughout this article, you can rest assure that you are better equipped than a large portion of other hunters on the mountain. It’s a huge advantage. In the West, hunting success can very much depend on your ability to negotiate mountain thermals.

Wind checkers are an absolute must. I always carry two and I wind check over a hundred times per day. It must be constant. My favorite is the one in the image, click on it if you want to grab a couple of them from Amazon.

Also, make sure you watch this video by Randy Newberg. He provides a visual aid in real time that show effects of not understanding thermals.

Lastly, perhaps the most comprehensive explanation of thermals can be found at the University of Elk Hunting from Elk101.com. You have to sign up and pay to go through the course, but it’s worth it. Sincerely. This is simply a kind recommendation, I receive no kick-backs for making it to you. However, since my wife has capped me on my 2019 hunting budget, if Corey Jacobsen reads this and wants to pay me, I really need a new bow buddy!

Good luck out there and as always, I sure appreciate the read!

See you on the mountain.

Jim Huntsman

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Ethan Smith is a seasoned marine veteran, professional blogger, witty and edgy writer, and an avid hunter. He spent a great deal of his childhood years around the Apache-Sitgreaves National Forest in Arizona. Watching active hunters practise their craft initiated him into the world of hunting and rubrics of outdoor life. He also honed his writing skills by sharing his outdoor experiences with fellow schoolmates through their high school’s magazine. Further along the way, the US Marine Corps got wind of his excellent combination of skills and sought to put them into good use by employing him as a combat correspondent. He now shares his income from this prestigious job with his wife and one kid. Read more >>