Across Europe this week, temperatures are reaching levels that push well beyond ordinary summer warmth into genuinely dangerous territory. In some regions forecast highs are exceeding 40 degrees Celsius, and for horse owners the question is no longer how to keep horses comfortable, it is how to keep them safe. Conditions like these are not simply an inconvenience to manage around. They demand a more immediate and considered response than a typical hot day.
If you are reading this while a heatwave is already underway, this post is for you. We have covered general summer management in our earlier guide, Beat the Heat, but this post is specifically about what to do when conditions escalate beyond normal summer heat and your usual routine is no longer enough.
Understand What You Are Dealing With
The distinction between a warm summer day and a true heatwave matters more for horses than many owners realise. When temperatures push above 35 degrees Celsius and humidity is high, the horse's primary cooling mechanism, sweating, becomes significantly less effective. Moisture does not evaporate readily from the skin in humid air, which means heat builds up in the body even when a horse appears to be sweating normally. A horse standing quietly in a field in these conditions is still under genuine physiological stress, and one in work can be at serious risk.
The Heat Index is the most useful tool for assessing actual risk on a given day. Add the air temperature in Fahrenheit to the relative humidity percentage. Once that combined figure reaches 180 or above, horses should not be in anything beyond the lightest exercise. Above 200, the only appropriate decision is a rest day. This is not overcaution. At these thresholds horses cannot cool themselves adequately through exertion, and the consequences of pushing through can be severe and fast moving.
If you are unsure of the current humidity level, most weather apps display it alongside temperature. Checking both before you ride, not just the temperature, is one of the most important habits you can build during a heatwave period.
Significantly Modify Work
This is the week to set competition preparation aside and prioritise your horse's welfare above all else. If the Heat Index is above 150, shorten and reduce the intensity of any ridden work significantly and schedule it for the very earliest part of the morning before the day heats up. If it is above 180, ride only at walk for a short period or rest the horse entirely. If it is above 200, do not ride at all.
The horses most at risk during a heatwave are those that are older or very young, horses carrying more weight than ideal, those with any underlying respiratory conditions, horses that have recently travelled, and horses not yet acclimatised to high temperatures. If your horse falls into any of these categories, the threshold for rest should be lower, not the same. Dark coated horses also absorb significantly more radiant heat from the sun than lighter ones, and should be monitored more carefully in direct sunlight.
Water: Check It More Often Than You Think Is Necessary
During a heatwave a horse's water requirements can reach 80 to 100 litres per day or more. That is not a figure that surprises most owners until they consider that a standard trough can be emptied by a small group of horses in a matter of hours in extreme heat. Checking water once in the morning is not sufficient this week. Check it at minimum three times a day, and more frequently if you have multiple horses or if troughs are on the smaller side.
Water temperature matters too. Troughs in direct sun can reach temperatures that horses find unpalatable, and a horse that does not like the taste or temperature of its water will not drink enough regardless of how thirsty it is. Moving troughs into shade, or adding ice to water buckets in the stable, can make a significant difference to intake. If you notice a horse that is not drinking as much as you would expect given the conditions, act on it promptly; dehydration in heatwave conditions can progress to serious illness quickly.
Keep Horses Out of the Sun During Peak Hours
In ordinary summer weather, adjusting turnout times is a sensible precaution. During a heatwave, it is essential. The period between roughly 10am and 4pm carries the highest UV and heat burden of the day, and horses left in exposed paddocks during these hours in extreme conditions are at genuine risk of heat stress even without any exercise at all.
Stabling horses through the hottest part of the day and turning out in the evening and overnight is the single most impactful management change you can make during a heatwave. If stabling is not an option and your paddocks have limited natural shade, a field shelter becomes critical rather than merely useful. Horses will use it if it is positioned well and the interior is not itself trapping heat.
For horses that must remain outdoors, a UV rated fly sheet or fly mask provides protection from radiant heat absorption as well as insect pressure. It may seem counterintuitive to rug a horse in extreme heat, but a high quality breathable UV sheet reflects more heat than bare skin absorbs in direct sunlight, particularly for dark coated horses. This is not true of heavier or non breathable rugs, which should absolutely not be used in these conditions.
Ventilation in the Stable Is Non Negotiable
A poorly ventilated stable in a heatwave can be significantly hotter than the outdoor temperature, which negates the benefit of bringing horses in at all. Every door, window, vent, and opening should be fully open during the day. Fans should be running in any stable that has them, positioned to direct airflow across the horse rather than simply circulating hot air. If your barn has a dark metal roof that absorbs heat, be particularly mindful of how warm the interior becomes during peak afternoon hours and factor that into your decisions about where horses are safest.
Some owners in severe heatwave conditions choose to wet the stable floor or use misting systems to cool the air. Both can help, though misting is more effective in low humidity conditions than high humidity ones. What matters most is that air is moving and the horse has access to cool, fresh water at all times.
Know the Signs and Act Without Hesitation
Heat stress in a heatwave context can escalate to heat stroke within minutes rather than hours. The early warning signs: elevated breathing rate, excessive sweating or a complete absence of sweat, reluctance to move, skin that feels very hot to the touch and should be treated as urgent rather than something to monitor and see how it develops. If you see these signs, act immediately.
Move the horse to the coolest available place, ideally shade with good airflow or a ventilated stable. Apply cool water continuously to the neck, the large muscle groups of the hindquarters, and the legs, scraping it off and reapplying rather than letting it warm on the coat. Use a fan if one is available. The goal is to lower the body temperature as quickly as possible, and this process should not stop until the horse is visibly recovering and vital signs are returning towards normal.
Call your vet immediately if the horse does not begin to respond within a few minutes, if you observe muscle tremors or unsteady movement, if the horse goes down, or if you are able to take a rectal temperature and it is above 41 degrees Celsius. Do not wait to see if things improve on their own. In a heatwave, heat stress can become heat stroke very quickly, and heat stroke is a veterinary emergency. It is worth having your vet's number saved and accessible before you need it, along with a basic understanding of your horse's normal resting temperature and heart rate. In an emergency, that baseline knowledge is genuinely valuable.
After the Heatwave Passes
Once temperatures return to more manageable levels, resist the temptation to immediately resume normal work. Horses that have been under sustained heat stress, even without showing acute signs, may need several days of light work and careful monitoring before returning to full training. Gut function in particular can be disrupted by dehydration and electrolyte imbalance, so watch droppings closely for changes in consistency and watch for any signs of colic in the days following extreme heat.
If your horse was visibly affected during the heatwave, a conversation with your vet before resuming work is worthwhile. Some horses, particularly those that have experienced heat stress before, can be more susceptible in future episodes, and understanding how your individual horse responded will help you manage the next one more effectively.
Heatwaves of this intensity are becoming more frequent across Europe, and as horse owners we are all learning to adapt our management in real time. The most important thing this week is to slow down, check in more often than feels necessary, and trust your instincts if something does not look right. Your horse cannot tell you they are struggling, but they will show you, if you are paying attention.
Please note: the guidance in this post is intended as a general reference. Every horse is an individual, and you as their owner are best placed to understand their specific needs, health history, and temperament. If you have any concerns about your horse's health or welfare, always consult your vet.