The short version of my previous post on how a long coat affects a dog when it’s hot outside

person touching golden retriever

This is the short version of my long blog post about clipping the dog short for the summer.

I have had several requests about a shorter version of my previous post about clipping the dog shorter for the summer.
This is an attempt to condense the facts I am trying to share in that post.
I urge you to read the long version -even if it feels boring 😉 But that will give you a much greater understanding on the subject.
Use this as a taster and then go on to the 2 long posts about the coats role in the thermoregulation process and the the effects of clipping the dog shorter for the summer. 🙂

The whole debate about whether the coat keeps the dog cool or not is based on several misunderstandings and a lack of knowledge about how the dog’s temperature regulation works. Its a complicated system and many factors that we must weigh in.

The temperature regulation works briefly as follows:

It’s just like a thermostat – the system kicks in when the dog gets too hot or too cold.
Puppies, old dogs and dogs with underlying health problems have less effective temperature regulation.

When the dog’s body temperature rises, the body sends warm blood to the superficial vessels on the skin – the heat radiates to the outside of the skin and the cooled blood then goes back into the body.
If that is not enough to bring down the core temperature, the dog also starts to sweat.

Dogs sweat through the foot pads and the skin. However, the sweating on the skin is not great and does not have much effect. The sweating in the pads is stronger but does still not have as much of an overall effect.
If this doesn’t help, the dog starts to pant. First with a slightly open mouth and then the mouth opens more and more, and the tongue hangs out more and more .
Panting cools because warm blood reaches the mucous membrane in the mouth and nose – there the heat radiates out and when it meets the cooler air, condensation forms which then evaporates. The evaporation process uses the heat and the cooled blood is transported back into the body.

When the temperature around the dog is above 32 degrees, the only cooling effect that has any real effect is panting.
However, panting has 2 weaknesses – the dog uses its muscles when it pants and muscle movements create more internal heat that the dog has to get rid of. It is also physically tiring for the dog.
When the temperature in the environment is high and there is also high humidity, the panting becomes ineffective because there is no heat exchange between the mucous membrane and air. 
It is also more difficult to breathe in high humidity as the air becomes thicker from all the liquid – so the body has to work harder for each breath, which contributes to even more internal heat being produced and an even more tired dog.
Then the dog is in real danger and will overheat.

The problem we have with the coat is that when the heat radiates from the skin, it gets stuck in the air gap inside the undercoat. This means that the dog is now surrounded by a warm bubble… It’s great when it’s winter and it needs to be warm.

This is a golden retriever, he is indoors and the temperature in the room is what you see first. And the next reading is from inside his coat.

But not so beneficial when it’s hot outside, as this scientific article points out:

“Contrary to the cold environments, increased insulation of fur is not beneficial to maintaining heat balance in warm environments. “

Seasonal changes in the heat balance of dogs acclimatized to outdoor climate 
Yasuyuki Sugano

That is why nature has made it so that they have a thick coat in the winter and shed to a thinner coat in the summer. 
The thinner and often shorter summer coat means that less heat is stored inside the coat as the air gap is smaller and the coat is more “open” so that wind and movements in the coat can release the heat.

The problem is that we have changed the coats because it is aesthetically pleasing with more hair and when we neuter the dogs on top of that, they get a thicker and longer undercoat that doesn’t shed as well as a natural coat.
Many are also overweight and the fat  insulates and makes it harder for the internal heat to  get out to the skin.

 This means that we in this discussion cannot categorically refer to nature’s plan with shedding, etc., as our breeding  has changed the dogs’ coats so that they no longer function as nature intended.
We have also moved dogs that are made for cold climates (with attached extra insulating coats) to warm climates that require thinner coats.

The whole issue is described very well in the book Hair loss disorders in domestic animals by Lars Mecklenburg, Monika Linek, Desmond J Tobin


Domestication can be associated with changes in hair density, hair length, hair thickness, hair structure, and hair colour eventually resulting in a hair coat that no longer can fulfil all its functions necessary for a typical life under normal outdoor conditions. These changes have been caused by genetic alterations in intensely bred animals such as the cat and the dog.


Swedish show champion born in 1928
This is a New Foundland, compare the amount of hair with how they look today, Today’s dogs are also heavier which requires more muscle activity when they move which gives more heat produced inside.

The dog has some areas of the body that have less hair and also thinner skin and large superficial blood vessels to try to compensate for the so effectively insulating coat – these are the ears, the front of the front legs and the lower part of the hind legs and belly. It is called a ” thermal window” where the heat can more easily leak out and disappear completely away from the dog. The body directs a lot of the blood there when it tries to get rid of the excess heat.

The coat does have an insulating effect – but the problem is that it insulates in both directions…
And this is where the misunderstanding has arisen –

The coat helps prevent immediate heating of the skin by the sun – but if the dog has long hair, the sun will heat the surface of the coat instead. If it’s windy, a lot of the heat will blow away. But if there is no wind, it quickly gets very hot on the surface and then that heat will find its way down into the coat even if it is cold in the air. (that’s how the laws of physics work – heat always goes towards the cooler area)

The air gap inside the coat initially protects the skin from being heated by the sun – but as the surface of the coat heats up, that heat will warm the air inside the coat.

You know how it can feel on a cold winter’s day – the sun warms you if you are protected from the wind and you can sit without a jacket when you are sheltered, but if it is windy, you do not notice much effect from the sun’s rays.

Heat always goes from warm areas to cold-it heats the surrounding cooler areas. So, if there is colder air inside the coat, the heat on the surface will heat it  and so the heat will find its way down to the skin and the dog is once again surrounded by a warm bubble . If the air inside the coat is warmer than the skin, it will heat the dog’s skin and the heat will travel in to the dogs body.

This is clearly illustrated in an experiment described in a scientific article – “The microclimate of the canine coat: The effects of heating on coat and skin temperature and relative humidity “

September 1997Veterinary Dermatology 8(3):183 – 190 Authors: CJ Chesney…/j.1365-3164.1997.d01… )

They had 6 border collies who were allowed to run around in a field on a sunny day. It was around 20 degrees outside.
When they measured the temperature inside the coat  it was between 35-40C inside …… So, 15-20 degrees warmer inside the coat compared to the environment…… even though there was probably a little wind plus the dogs were moving so the coat was moving and opening up to allow for some heat to disappear out into the environment.

Another experiment was also done with 6 Newfoundland dogs. They were indoors. An infrared lamp was switched on above the dog and after a while, the heat created on the surface crept into the coat and when it was over 41C inside the coat the experiment had to be stopped because the dogs were significantly negatively affected/stressed by the heat.

So no – the coat does not catch cold air – where would it get the cold air from if it is 30C outside?
The air inside the coat will be heated by the heat from the skin AND from the heat in the environment/coat surface .

If we clip the coat shorter, the heat can leave the coat more easily and the dog, therefore, stays cooler. It’s just a matter of not scalping the dog – some hair is needed to protect the skin.

The following scientific articles all state the same thing – lots of hair keeps the dog warm:

Contrary to cold environments, increased insulation of fur is not beneficial to maintaining heat balance in warm environments. “

Seasonal Changes in Heat Balance of Dogs Acclimatized to Outdoor Climate Yasuyuki Sugano…/31_4_465/_article/-char/ja/

Clipping the coat short decreases its insulating abilities by 50% and makes it easier for the dog to dissipate the heat (Predicted thermal responses of the military working dog (MWD) to chemical, biological, radiological, nuclear (CBRN)protective kennel enclosure by Larry G. Berglund, Ph.D.Miyo Yokota, Ph.D.William R. Santee, Ph.D.Thomas L. Endrusick, BSAdam W. Potter, BAMAJ Scott J. Goldman, VMD, Ph.D.Reed W. Hoyt , Ph.D.…/279517419_Predicted… )

“Predisposing factors for heatstroke
-thick haircoat”

Short technical Report on Thermoregulation in Dogs and the Pathophysiology of Hyperthermia Jerilee A. Zezula, DVM

“Predisposing Factors for Heatstroke
– thick haircoat”

Heatstroke – thermoregulation, pathophysiology and predisposing factors Carey Hemmelgarn DVM ChristI Gannon DVM DacVecc…/heatstroke-thermoregulation… ;

“Factors that inhibit heat dissipation:
Thick, dense coat – increased insulating effect”

Hyperthermia and Heatstroke in the Canine
Lori E. Gordon, DVM…/Hyperthermia-and…

“Well-insulated breeds with thick fur and fat may struggle to maintain a normal body temperature,especially during hot summer days and in a warm ambient environment.“

Hyperthermia during anaesthesia
Author : Clara Rigotti, Marieke De Vries 2010…/hyperthermia-during… ;

“Well-insulated breeds, such as Chow Chows and St. Bernards, may struggle to maintain normal core body temperature, making them more prone to hyperthermia, especially in a warm, stressful environment”

Hypothermia in a chow chow under general anaesthetic
H.Jones, K.Robson ,2022…/vrc2.423

“Predisposing factors that decrease heat dissipation:
Hair coat – Thicker coats decrease radiation and convection”

Heatstroke in small animal medicine: a clinical practice review
Scott I. Johnson, DVM, Maureen McMichael, DVM, DACVECC and George White, DVM…/j.1476-4431.2006.00191.x

“Another group of dogs needing special consideration for temperature ranges are those with extremes in coat type, both those with particularly thick coats, such as Siberian Huskies, and those with thin to absent coats, such as Chinese Crested dogs. Thicker coats decrease heat loss from the skin (Johnson et al., 2006). Without proper attention, such dogs may face thermal distress at higher temperatures than might be acceptable for other dogs”

Temperature requirements for dogs
Mary Jordan, Amy E. Bauer, Judith L. Stella, Candace Croney
Department of Comparative Pathobiology, College of Veterinary Medicine
Click to access va-16-w.pdf

” a thick insulating pelage is a disadvantage in situations where energy supply is unlimited and expenditure is constrained by the capacity to dissipate body heat.
This is because the pelage insulation becomes the primary constraint on heat loss. 

Maximal heat dissipation capacity and hyperthermia risk: Neglected key factors in the ecology of endotherms, Journal of Animal Ecology  79(4):726-46 J. Speakman, E. Krol

The bottom line is – lots of hair keeps the dog warm – less hair makes it cooler.

However, all dogs are individuals and react differently to the heat depending on age, condition, state of health and individual preferences.
That’s why we can’t say -this is what you must do….

My standard poodle doesn’t tolerate much heat at all, he gets affected when it’s 15C and he has a 4 cm long coat.
The video below shows how warm it is inside his coat.

Its 20C in the room and 30C inside his coat….

My fox terrier on the other hand ,would sleep on top of my stove  when the fire is lit if I allowed her 🙂 

If you decide to clip the dog shorter ,don’t make it naked – the skin can be damaged by the sun and they also need protection from insects and the weather..
The skin gets dried out by the sun and wind – just like our skin and that can lead to thickened skin and a reduced regrowth of the coat. Use common sense and leave a couple of centimetres as a  protection.

Clipping double coated breeds

The issue we have when we talk about this subject is that  some coats can grow back ugly and uneven when we clip them. This means that we must weigh the pros and cons when we decide whether to clip them or not.  

This applies to the so-called double-coated breeds. Their hair growth cycle has a very long resting phase, which means that the guard hairs grow for a short period and then they are stuck in the hair follicle but do not grow for 2-5 years. If you then cut them off, there will be no growth of the hair if it is in the resting phase,  nothing will happen until the dog sheds that guard hair and a new one grows out.
All the guard hairs are in different phases all over the body and this is what makes it look so uneven when it grows out.
Some guard hairs were at the beginning of the growth phase when you clipped it – others at the end – some at the beginning of the resting phase – others at the end.
The Arctic breeds have a resting period of 4-5 years, so it can take a very long time before the coat looks normal again and we should avoid clipping them short if possible.

Golden retrievers, collies and similar breeds usually grow back ok in 6-8 months if you only clip them once a year and the dog has no underlying disease/is old – if they are clipped regularly, there may be an more uneven and longer growth period,as you constantly clip off the new guard hairs and finally there is nothing to cover the wool.

The undercoat, on the other hand, has a much shorter cycle – they shed and get a new undercoat twice a year and this means that the dog gets a lot of fuzzy wool and then sparse guard hairs here and there.
They don’t get a thicker undercoat ,it just look like that as we suddenly can see it full on without the cover of the guard hairs.  But the undercoat can be damaged and mat more without the protection of the guard hairs, so we must make sure its well conditioned during the re growth of the guard hairs. 

Collie shaved with a 5F every 4th month

The same dog. This is how he looks every 2nd year ,4 months after his groom.

The dog’s health must come first – sometimes it can be enough to shave the belly and under the chest and shorten the coat on the front of the neck and the back of the pants , in combination with a proper de-shedding to make the dog feel better.
The body will now have a chance to release excess heat through the “windows” on the belly and neck and the thinner coat. You can also clip the ears shorter.

If it is only a short period of heat, you can cool the dog by soaking it right into the skin during the hot days and making sure that the dog is in the shade and does not exercise when the sun is out. The evaporation process will cool down the skin and hopefully keep the dog comfortable.

But if the dog is overweight, elderly, suffer from some kind of chronic disease or is just generally sensitive to heat, more drastic measures may be needed to make it feel ok.
Then we must look past the aesthetic and put the dog’s welfare first and a short haircut will make the dog feel much better. But again – don’t shave it down to the skin – leave a couple of centimetres so the skin is protected.

We can mitigate the effects of the haircut by doing proper de-shedding before we clip the dog short. Then we imitated nature’s shedding and moved as many hair follicles as possible to the growth phase and thus reducing the risk of uneven growth.

We must look at the individual and make an assessment based on the individual dog’s conditions instead of just saying categorically NO when it comes to double coated breeds !

If you want to read a more detailed description of how the temperature regulation works, a discussion of the pros and cons of clipping and why we see changes in the coats when we clip certain breeds – go to my other post on the subject that is much more in dept.  Read more…

And here is a post that dives deeper into the coats role in the dogs thermoregulation   Read more…

Here are some references to the facts I have shared in the post

Books to read:
Muller&Kirk – Small animal dermatology
P.Withers,C.Cooper,S.Maloney,F.Bozinovic -Ecological and Environmental Physiology of Mammals
K.Schmidt-Nielsen- Animal physiology, adaptation and environment
Guyton and Hall -Textbook of Medical Physiology 

Wikipedia – Temperature regulation
Wikipedia – Heat transfer 

Some of the scientific articles I gathered facts  from that are not already linked in the post:

Heat Production and Heat Loss in the Dog at S-36°C Environmental Temperature
H. T. Hammel, CH Wyndham, JD Hardy

A model of sensible heat transfer across the boundary layer of animal hair coat KG Gebremedhin Agricultural Engineering Department, Cornell University, Ithaca, NY 14853, USA

Hair coat characteristics in Friesian heifers in the Netherlands and Kenya by H.Veenman

The effect of clipping the coat on various reactions of calves to heat. By W.Bianca

The effect of coat clipping on thermoregulation during intense exercise in trotters
K. Morgan, P. Funkqist ,G. Nyman

Spaying-induced coat changes: the role of gonadotropins, GnRH and GnRH treatment on the hair cycle of female dogs Iris Margaret Reichler*, Monika Welle†, Christine Eckrich*, Ursula Sattler†, Andrea Barth*, Madeleine Hubler*, Claudia S .NettMettler‡, Wolfgang Jöchle§ and Susi Arnold.

Effective thermal conductivity of the hair coat of Holstein cows in a tropical environment Alex Sandro Campos Maia2, Roberto Gomes da Silva3, João Batista Freire de Souza Junior2, Rosiane Batista da Silva2, Hérica Girlane Tertulino Domingos

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