Why Does Snow Melt Around Trees First? & Why It’s a Serious Danger to Skiers

by Robert Stanley | Updated: October 27th, 2022 |  Skiing Articles

When I was a child, I always wondered why the snow always seemed to melt around trees before anything else.  Why not on the bushes and the grass?  As I grew older, I thought less about this until I started skiing. So why does it happen?

Heat energy is absorbed around the base of the tree causing it to melt.  The dark color of the trunk absorbs energy from the sun resulting in deep holes or depressed layers of snow around the trunks.  This is particularly noticeable after a snowstorm.

Brokeoff Caldera

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As more snow melts, circles begin to appear on the ground around the base of the trees.  Although this occurs, a blanket of snow continues to cover the remainder of the ground since open areas do not gain much of the sun’s energy because of the high reflection.

Snow Wells and How They Affect Skiing

Kepler Cascades Trail
Photo by Yellowstone National Park licensed under Public Domain Mark 1.0

Skiing is one of the most exciting and exhilarating sports around.  Slicing through the powdery white snow gets your blood pumping and makes you feel the need for speed.  But deciding to leave the slopes for trails can bring a new set of obstacles.

Skiing close to trees has always been considered dangerous but even more so with the risk of encountering snow wells.  Snow wells are deep areas of unconsolidated snow that skiers fall in and become unable to move or suffocate. Deaths caused by these horrible accidents are called SIS hazards or Snow Immersion Suffocation.

If you decide to leave the safety of the trails or slopes, you agree to take the risk of a possible snow immersion accident. Do not attempt this without knowing the risks.

So What Exactly is a Tree Well?


A tree well is a deep hole or depression that forms around the base of a tree.  These voids often contain mixtures of low-hanging branches, loose snow, and air.  Certain evergreen trees such as firs, hemlocks, and more can develop when low-hanging branches block snow from filling in and building up around the tree's base.   The low-hanging branches often hide these deep wells from view. 

Since there is no way to easily identify if a particular tree is dangerous or not, it is in your best interest to assume that ALL trees and tree wells are dangerous.

It is also good to remember that since tree wells will always be next to a tree, it is easy to avoid these areas.

What Happens When You Fall in a Tree Well?

Thigh deep in powder
Photo by Ruth Hartnup licensed under CC BY 2.0

SIS accidents tend to occur when a skier falls headfirst into a tree well or in deep loose snow.  When you land in an inverted position, you can become trapped under the snow which makes breathing difficult because the loose snow packs in around you.  If you do not have a partner close by for immediate help, it is very easy to suffocate. 

Learning to prevent SIS accidents is very important because the survival odds of a deep snow immersion are extremely low. In fact, 90% of people involved in Tree Well/SIS hazard experiments were unable to rescue themselves without the aid of a partner.

Tips to Avoiding Tree Wells and SIS Accidents

Roller Coaster Trail
Photo by Yellowstone National Park licensed under Public Domain Mark 1.0

The best way to reduce the risk of SIS hazards is to become aware of your own actions and awareness of the terrain.  It is advised to ALWAYS ski with a partner within viewing distance.  

Always check with the local resources so that you are aware of how deep the loose snow is and, when able, remain on the groomed ground.  This will help you avoid potentially dangerous snow and tree wells. If the call of ungroomed terrain is too much to resist, here are some other safety tips to keep in mind when skiing:

  • Always ski with a partner
  • Always keep partner in sight – most victims of SIS accidents are rescued by their partner
  • Maintain control while skiing
  • Look for open spaces between trees and not directly at the trees
  • Remove ski pole straps
  • Always carry safety equipment including:
  • Cell phone with emergency contact numbers (resorts typically have one)
  • Whistle
  • Beacon or transceiver
  • Avalung
  • Shovel
  • Keep in mind that awareness and education significantly reduce the risk of an SIS accident. 

What to Do When an SIS Accident Occurs


No one wants to think about having an accident when skiing, but it is best to always be prepared.  If an accident does occur, these are some helpful tips to help get you out of trouble:

  • Whistle or yell for your partner
  • Do your best to keep your head above the surface of the snow – this might mean grabbing branches or the tree trunk itself.  Do your best to keep your feet below your head.
  • If the snow does begin to cover you, make space around your face to protect your airway.  Try not to struggle – this could affect your airspace and make the immersion worse.
  • Conserve air by remaining calm
  • Have faith that your partner is on the way
  • If able, use a cell phone to contact the resort’s emergency number or the ski patrol

What To Do if You Are The Partner In AN SIS Accident


No doubt about it, seeing your partner fall into a tree well is frightening!  The first thing to remember is if you lose sight of your partner, automatically assume that they need help.  In addition, the partner should always remember:

  • NEVER leave to go get help – always stay with your partner
  • Check the safety of the area for yourself
  • Call for help  - the ski patrol or the resort’s emergency number are the best bets
  • Begin snow immersion rescue efforts immediately
  • Determine where the victim’s head is and tunnel from the side – NEVER attempt to pull them out the way they fell in

The next time you see the snow melting at the base of a tree, hopefully, you will remember that this innocent-looking act of nature can cause life-threatening injuries or death. 

Snow immersions and Tree Wells should be taken seriously.  Following basic prevention guidelines and carrying the proper rescue tools will help keep you slicing effortlessly down the slopes.