What temperature is too hot for horses? How hot can horses tolerate? When is it too hot to ride a horse?
So far in the UK, we haven’t really had to be too concerned with heat, but with the Met Office (UK) being quoted last week as saying there is a “greater than normal chance” of heatwaves in the UK this Summer, it won’t be long before these sort of questions start to pop up on social media every summer. And whilst there is no answer that applies to every single horse, there are, as you might expect, some general rules.
Generally speaking, many breeds of horses are well adapted to dealing with heat. In fact, of course, there are breeds like Arabians and Thoroughbreds which cope very well with heat, whilst at the other end of the scale, heavy breeds such as Shires, Icelandic ponies and Norwegian Fjord horses which thrive in cold climates. So, the basic principle here is obvious, thick-coated, stocky or large breeds do well in cold and “finer” short-coated breeds do well in hot weather.
Just like people, even within the same breed, there are some individuals who cope better with heat than others. Very young and old horses, unfit horses, those carrying excess body fat and those with long-term health conditions such as equine asthma, Cushings, muscle disease or heart disease will find heat more of a challenge.
So what do we call hot? 25°C? 30°C? 35°C? To a large extent, it depends on the individual horse and what it is “used to”. In scientific terms, we call this acclimatisation. For example, if the temperature has been 30°C for a month and you have been riding in the hot part of the day for a month, then your horse or pony will probably cope well because it is used to the heat or acclimatised. However, if its been 15°C for the past month and suddenly the temperature shoots up to 25°C, then this could be a significant challenge. So a key point here is how your horse copes with heat depends on how long its had to adjust. Also, even if its been 30°C for the past few weeks and you ride early in the morning when its say 20°C, your horse will not be acclimatised to 30°C just by standing around the rest of the day in the warm. The majority, probably over 90% of the acclimatisation effect to heat, comes from training in the heat – getting the horse warmer than it would normally get.
When we ask “What temperature is too hot for horses?” or “How hot can horses tolerate?” or “When is it too hot to ride a horse?”, most of the time this will be in the context of just air temperature. It’s worth being aware of the fact that “heat” or “thermal stress” is actually a combination of factors, of which air temperature is only one. We also have to consider humidity. Horses are able to sweat to cool themselves down and can sweat 3x faster than ourselves, even allowing for the obvious difference in size. But as the humidity increases, the rate of sweat evaporation and therefore cooling decreases. We also have to consider the sun or solar radiation. The heat “load” on a horse on a day with a cloudless sky will be significantly greater than on an overcast day. Finally, still days also add to the heat load on the horse as a breeze or wind increases evaporation of sweat and the cooling of the horse.
The best advice for dealing with heat is to avoid it. If you can, ride early in the morning or late in the evening. But if you are going to compete and many competitions obviously take place during the day, then it will be a huge advantage to train during the warmer part of the day for several weeks. This will improve your horses’ performance and also greatly reduce the risk of heat-related illness. And of course, clipping also makes a huge difference.
If you are riding in the heat, then be aware that your horse’s ability to cope, even when acclimatised, will be less than in cool weather. Be prepared to ride slower and or for shorter periods. Look at your horse. If he is dripping with sweat, hot to touch and blowing hard, then he is hot. Make preparations to cool your horse effectively, especially if you are away from home. Cold water hosing all over is probably the most practical and effective way to cool a hot horse. Remember to run the hose first to check the water temperature if the hose has been lying in the sun. It may take 20 minutes of continuous cold hosing to recover your horse. The best indication of recovery is your horse’s breathing. If they are blowing hard or panting, then they are still hot. If you don’t have the facilities to cool your horse at home or at competition, then you probably should not be exercising your horse in the heat.
So to answer the questions, “What temperature is too hot for horses?”, “How hot can horses tolerate?” and “When is it too hot to ride a horse?”, it depends on the individual horse, it depends on what the weather has been recently, it depends on what you are planning to do, it depends on whether you have the facilities to cool your horse off effectively afterwards and the best guide is looking at your horse to see how they are coping!