Like other mammals, a horse wants to maintain a stable body temperature. This is easy when the outside temperature falls within the so-called "thermal comfort zone." In that range, the horse does not need to use extra energy to stay warm or cool down.

A different comfort zone than humans

The comfort zone for horses is lower than for humans. An unclipped horse has no problems with temperatures between 5 and 25 °C. That means at 10 °C and dry weather, your horse won’t be cold, even though it may feel chilly to you. On the other hand, while 28 °C feels pleasant to us, it is already quite warm for a horse.

Cold

When temperatures drop, blood vessels in the extremities, such as the ears and legs, constrict to keep the body core warm. Cold ears do not mean the horse is cold – it’s just a protective mechanism. Similarly, when the hairs stand up, they trap air, forming an insulating layer like a down jacket. A horse that is truly cold will start shivering. Shivering increases muscle activity, which generates heat. Movement and extra forage also help, since the hindgut produces heat during fiber fermentation. If temperatures drop gradually, horses adapt by growing a thicker coat, using feed more efficiently, and redistributing body fat. Sudden cold spells, however, are harder to cope with.

Losing weight in winter

In nature, horses gain weight in summer to build reserves, which are then used in winter. Owners often prefer to keep their horses at a steady weight, especially when training them. That’s why providing enough high-quality forage is key. If your horse still loses weight in the cold despite sufficient hay, a rug might help – especially for older horses with slower digestion. But in general, horses in the Netherlands are often over-blanketed, which can be uncomfortable and unhealthy. Always look at your individual horse. If in doubt, check his body temperature (normally between 37.5 °C and 38.2 °C).

What about rain?

In autumn, rain and wind add to the challenge. The wind chill can make it feel colder than the thermometer shows. Whether your horse gets cold depends on its coat. Icelandic and Shetland ponies grow thick coats that protect against rain and wind. Unclipped horses with dense winter coats can usually cope down to -8 °C. Clipped horses or those with thinner coats may get cold when wet, especially with strong winds. A dry shelter is essential. A rain rug can help, and studies have shown that many horses actually choose a rug in cold, wet, and windy conditions. For clipped sport horses, a rain rug is necessary. However, do not over-rug. In autumn, a rain rug is usually enough; only when temperatures drop well below 10 °C should you consider adding a lining. Always base your choice on your horse’s individual needs – and when in doubt: measuring is knowing. After training, let your horse cool down before putting the rug back on.