Heat Stroke Symptoms: Warning Signs and Emergency Care

Heat stroke needs a fast response. This guide explains warning signs, emergency cooling, medical assessment and practical ways to reduce risk.

While help is coming, move the person to a cooler place if safe, wet their skin with cool water and fan them. ²⁶

Educational information checked against the listed sources on 14 October 2026. It cannot diagnose an individual or replace emergency care. Read our medical disclaimer.

What is heat stroke?

Heat stroke develops when the body cannot release enough heat to keep its internal temperature under control. Heat comes both from the environment and from the body’s own activity. Sweating and increased blood flow near the skin normally help remove it, but humid air, intense exertion, heavy clothing and limited air movement can make that process inadequate. The resulting overheating can damage organs and become life-threatening. This is more serious than simply feeling uncomfortable on a hot afternoon. Heat also strains the heart and kidneys before someone necessarily develops the full emergency picture. Prevention therefore involves changing exposure and activity as well as paying attention to symptoms. Access to a cooler place matters; water alone cannot make an overheated environment safe. ¹

Clinicians distinguish exertional heat stroke, associated with strenuous physical activity, from classic heat stroke, associated mainly with environmental exposure. Athletes, workers and military personnel may generate large amounts of internal heat while exercising or working. A person resting in a very hot home can also become dangerously overheated without vigorous activity. Physical fitness does not make someone immune to exertional illness. The ACSM consensus emphasizes recognizing risk, reducing avoidable exposure and planning an organized response wherever demanding activity occurs. The useful question is what combination of workload, conditions, clothing and individual health is present today. Yesterday’s successful workout does not establish that the same session is appropriate today. A change in weather, illness, equipment or intensity should prompt a fresh assessment. ⁸

Heat stroke symptoms: changes in thinking are a major warning

Look for a person who becomes confused, speaks unclearly, behaves unusually, cannot coordinate movements, has a seizure or loses consciousness after heat exposure. They may also feel extremely hot, have a fast pulse or develop a headache. Skin may be dry or very sweaty, so checking for sweat cannot rule heat stroke out. Do not expect every symptom to appear or follow a predictable order. A bystander may notice altered behavior before the affected person recognizes a problem. Treat these changes as an emergency even when the person is young, was previously well or insists that they can continue. ²

How heat exhaustion differs

Heat exhaustion commonly causes heavy sweating, thirst, weakness, dizziness, headache, nausea and cramps. Someone may look pale or feel clammy and struggle to keep going. Stop the activity, move to a cooler place, remove unnecessary outer clothing and begin cooling. A person with uncomplicated exhaustion should remain able to respond normally, although a lay observer cannot reliably sort every heat illness into a category. New confusion, seizures, marked loss of coordination or reduced responsiveness should trigger emergency help immediately. Do not wait through an observation period to see whether those signs settle. If an alert person’s symptoms worsen, they are vomiting or they are not improving with cooling, seek medical help promptly. Feeling slightly better does not justify returning straight to the heat. ³

What to do immediately when heat stroke is suspected

Call for help while cooling starts

Call the local emergency number and say that you suspect heat stroke. Give the exact location, including an entrance, trail marker or landmark that helps responders find you. Describe whether the person is awake and breathing normally. If others are present, one person can make the call while another begins cooling and someone else guides the ambulance crew. Stop the activity and move the person out of the heat when this can be done safely. Do not leave them alone or ask them to walk a long distance to reach help. OSHA advises responders to act without spending time deciding which heat illness is present. A workplace supervisor, coach or family member should not substitute a ride home for emergency assessment when neurological warning signs are present. ³⁰

Use cold-water immersion when it can be done safely

The 2024 AHA and American Red Cross first-aid guideline supports prompt neck-down immersion in cool or cold water for heat stroke when it is feasible and safe. This can be a first-aid measure, not solely a hospital treatment. Keep the head and airway above water, provide continuous support and never leave the person alone. Do not attempt immersion if you cannot prevent submersion or manage their movements safely. Use another cooling method immediately instead. The emergency call must already be underway; gathering a particular container or finding ice must not delay help. Follow dispatcher instructions and allow responders to take over cooling and monitoring. ⁴

If immersion is not feasible, wet the skin and fan

Use the cooling resources immediately available. Soak broad areas of skin or clothing with cool water and fan the person to help heat escape. Remove unnecessary clothing or equipment when it can be done safely, while protecting dignity and avoiding delays. Continue checking responsiveness and breathing as you cool them. If the person becomes drowsy, vomits or cannot protect their airway, tell the dispatcher at once and follow their positioning instructions. A person lying in water requires particular vigilance; change the method if you cannot keep the airway safe. Cooling and emergency communication should proceed together. Do not stop because you have applied one small cold cloth, and do not spend several minutes looking for an ideal setup while no cooling is happening. ²⁶

If the person is unresponsive or having a seizure

For an adult who is unresponsive and is not breathing normally, including only gasping, begin CPR and use an automated external defibrillator if one is available. Put the emergency call on speaker and follow the dispatcher’s instructions. Ask someone else to bring the AED; turn it on and follow its spoken prompts. A lay rescuer should not delay CPR by trying to find a pulse. Effective resuscitation takes priority when breathing is absent or abnormal. If the person is unresponsive but breathing normally, follow dispatcher guidance on keeping the airway open and positioning them safely while cooling continues. Keep watching because breathing can change. Tell responders immediately about any loss of responsiveness, CPR performed or AED instructions received. ²⁷

During a seizure, clear nearby objects that could cause injury and protect the person’s head. Do not hold them down, force their mouth open or place anything between their teeth. Give no food, drink or tablets. Note when the seizure began if you can do so without distracting from safety. A seizure following heat exposure is already an emergency, so do not wait for it to reach a particular duration before calling. When movements stop, check breathing and follow dispatcher instructions for airway care, positioning and continued cooling. Avoid putting a person with uncontrolled movements into water if you cannot keep the head and airway safe. Describe the event to responders even if the person seems more settled afterward. ³¹

Drinks are only for someone who can swallow safely

For heat exhaustion, a fully alert person who can swallow normally may take small sips of a suitable drink while resting and cooling. Water is acceptable; do not force large amounts. Stop giving fluids if they vomit, become drowsy, appear confused or have trouble swallowing. Nothing should be put into the mouth of an unconscious person. These restrictions matter because liquid can enter the airway when someone cannot protect it. Suspected heat stroke requires emergency cooling and assessment, and a sports drink cannot replace either. Tell the dispatcher if the person cannot drink or keep fluids down. Keep checking their condition rather than assuming that finishing a bottle means the problem has resolved. A change in responsiveness changes the urgency of the situation. ⁵

How clinicians assess and treat heat stroke

Assessment and cooling happen together

Clinicians use the history of heat exposure, physical activity, mental status and examination to recognize heat stroke. A reliable core temperature helps them assess severity and monitor treatment, but cooling must not wait when the clinical picture is concerning. In exertional cases, trained personnel may use rectal temperature because surface measurements can be misleading. This is a clinical procedure, not a step a bystander must perform before calling for help. Temperature can also have fallen by the time someone reaches care after cooling has begun. Describe what happened earlier, including confusion or collapse that has improved. Heat stroke can develop abruptly without a clearly recognized exhaustion phase. The absence of a long warning period therefore does not make a sudden episode less concerning. ⁶

Hospital investigations look for complications and other possible explanations while urgent treatment continues. Blood tests can assess electrolytes and evidence of muscle injury; urine testing and other investigations help evaluate the effects on the body. The team may repeat tests because a single initial result does not describe the whole course of illness. Tell them about recent exercise, time spent in heat, current medicines and any cooling or drinks given before arrival. If you are accompanying the patient, an accurate timeline is more useful than a guessed diagnosis. Mention a possible fall, injury or other exposure as well. Ask which findings need further monitoring and how results will be communicated. Testing supports care; it is not a reason to postpone cooling in a suspected emergency. ^{32, 20}

Why continued monitoring matters

Severe overheating can trigger inflammation and injury affecting several organs. The brain, muscles, kidneys, liver, lungs and heart may be involved, and problems with blood clotting can occur. The effects vary between patients, which is why outward improvement alone cannot establish that the episode is over. Medical teams assess organ function and provide support according to the abnormalities they find. Other conditions, including infection, neurological illness or drug effects, can produce overlapping symptoms and may need investigation. Family members should report what they actually observed instead of deciding that heat explains every change. Emergency clinicians can address both overheating and alternative causes. After a serious episode, follow-up should reflect the complications identified during admission, rather than a generic promise that everyone recovers within a fixed number of days. ²⁸

Fever medicines do not treat heat stroke

Heat stroke is not managed by taking a medicine ordinarily used for an infectious fever. The Society of Critical Care Medicine’s 2025 guideline favors active cooling and advises against using acetaminophen, also called paracetamol, NSAIDs or salicylates to lower temperature in heat stroke. These products do not correct the underlying heat overload and can add risk. Emergency and hospital teams may use fluids and other supportive treatments according to circulation, blood tests and organ function. That is different from trying a tablet and waiting at home. Do not give a confused person any medicine by mouth. If a medicine was taken before help arrived, tell the team what it was and when it was used so they can include it in their assessment. ²⁵

Muscle pain and dark urine need attention

Rhabdomyolysis is muscle breakdown that can occur with severe exertion or heat exposure. Warning symptoms include muscle pain or cramps beyond what the activity would normally explain, unusual weakness and urine that looks like tea or cola. A person does not need to have every sign. These symptoms can resemble ordinary soreness, dehydration or heat cramps, so appearance alone cannot confirm the cause. Seek medical attention immediately and describe the exertion and heat exposure. A blood test helps clinicians determine whether muscle injury is present, and tests may need repeating. Do not resume training simply because urine looks lighter after drinking. Make sure the clinician knows about demanding work or exercise in the preceding days, not just what happened immediately before symptoms became obvious. ²⁰

Recovery and returning to work or sport

Return to activity after heat stroke should be directed by the treating clinician and, when relevant, an athletic trainer or occupational health team. The NATA position statement describes medical clearance, recovery of organ function and a gradual return rather than immediate full training. The plan depends on the episode and the person’s response; it cannot be replaced by a universal number of rest days. Ask which symptoms or test results must resolve before progression, who will supervise the return and what to do if problems recur. Work duties, protective clothing and outdoor conditions may need adjustment as well as exercise intensity. A previously tolerated workload should be rebuilt carefully. Report lingering fatigue, reduced exercise tolerance or other changes instead of treating them as something to push through. ⁷

Who needs extra protection in hot conditions?

People with heart disease

Heat increases the demands placed on the heart and circulation as the body tries to shed warmth. For someone with cardiovascular disease, heat may worsen heart failure or contribute to other serious cardiovascular problems. Humidity and poor air quality can add to the burden. Make a hot-weather plan with the care team before temperatures rise, especially if activity or fluid intake is already restricted. The plan should explain how to adapt daily routines and which symptoms require urgent help. Chest discomfort, severe breathlessness or sudden neurological changes should not be dismissed as ordinary heat discomfort. Cooling access and practical assistance matter alongside medical advice. Our cardiovascular health guide explains the wider range of heart and blood-vessel conditions and warning signs. ¹⁰

People living with diabetes

Diabetes can make hot weather harder to manage. Damage to nerves or blood vessels may affect sweating, while dehydration and higher blood glucose can reinforce one another. Heat can also affect insulin, glucose monitors, pumps and test strips. Follow the storage instructions for your own products and keep supplies out of a hot vehicle or direct sunlight. Discuss monitoring and any treatment adjustments with your diabetes team rather than making changes based on a general article. A hot-day plan should also cover what happens if electricity or refrigeration fails. Carry the supplies needed to follow your existing care plan when away from home. Our type 2 diabetes guide provides background on everyday monitoring and follow-up. ²⁹

People taking medicines that affect heat tolerance

Some medicines change sweating, thirst, circulation or fluid balance, making heat exposure more difficult to tolerate. Examples include certain diuretics, anticholinergic medicines and psychiatric medicines; the effect depends on the particular drug, combination and person. Over-the-counter products also belong in the review. Ask a clinician or pharmacist to check your full list and prepare a clear plan for hot days. Do not stop, skip or change a prescribed medicine on your own. If adjustments are recommended, write down exactly when they apply and when the usual schedule should resume. Ask about storage as well, because excessive heat can damage some medicines and devices. Include any practical difficulty reaching a cool place or obtaining fluids so the advice fits your circumstances. ⁹

Older adults and people needing daily assistance

Older adults may experience greater strain from indoor heat without reporting how unwell they feel. Frailty, illness and limited ability to change surroundings can make this particularly dangerous. Health Canada’s 2026 guidance emphasizes protecting older people from sustained overheating indoors, including overnight. Its temperature recommendations are public-health planning tools, not a guarantee that a particular room is safe for every individual. Agree on regular contact with someone who can notice changes and arrange help. A check-in should establish whether the person can access a cooler room and carry out their usual activities, not just whether they answer the phone. If cooling equipment fails, have a realistic alternative that includes transport and any mobility needs. Waiting for someone to complain may miss a developing problem. ¹²

Pregnancy

Pregnancy changes the demands on the cardiovascular system, and heat exposure can add stress. CDC guidance links high heat with health risks during pregnancy and recommends planning protective actions with the maternity team. This does not mean that every warm day causes harm or that ordinary activity must always stop. It means exposure, underlying conditions and practical access to cooling deserve attention. Schedule demanding outdoor tasks for cooler conditions when possible, take breaks and discuss persistent symptoms promptly. Vomiting or diarrhea can make maintaining fluids more difficult. Know both the general heat-emergency signs and the pregnancy warning signs your team has explained. Workplace adjustments may be helpful where long periods of standing or physical work in heat are unavoidable. Individual advice should account for the pregnancy and any other conditions. ¹¹

Children and adolescents

Children rely on adults to make activities safer and to recognize when a child is struggling. Young athletes may keep going because they do not want to disappoint teammates, and younger children may not ask for a break or drink. Heat exposure also occurs during marching band, outdoor chores and activity in poorly cooled indoor spaces. The American Academy of Pediatrics advises gradual adjustment to hot-weather activity, adult supervision and an emergency plan. Adults should make it acceptable to report symptoms and stop without punishment. Ask who monitors conditions, where children can cool down and how parents will be contacted. Protective equipment and closely spaced practices can increase the challenge. A child’s enthusiasm for an activity is not a reliable measure of whether the conditions are suitable. ¹³

Children in vehicles

Never leave a child alone in a vehicle, even briefly. Parking in shade or opening a window does not make an unattended car safe. Heat can build quickly, and a child may also enter an unlocked vehicle and become trapped. Check the entire passenger area before locking up, keep keys out of children’s reach and establish a dependable reminder whenever the usual transport routine changes. Agree with a childcare provider on what to do if a child does not arrive as expected. If you see a child alone in a locked car, call emergency services immediately and follow instructions. A child in heat distress needs rapid rescue and cooling. Do not assume another passerby has already called or wait for the driver to return before acting. ¹⁴

Preventing heat illness: match the plan to the setting

Read more than the air temperature

A weather forecast’s temperature does not capture every part of heat stress. The heat index combines air temperature with humidity and is calculated for shade and light wind. Direct sunshine can make exposure more demanding than that number suggests. Wet-bulb globe temperature, often used for sport or work, also reflects factors such as radiant heat and air movement. Neither measurement is a personal diagnosis or permission to ignore symptoms. Choose the tool appropriate to the activity and follow local warnings and organizational policies. A reading from a distant weather station may not represent a sheltered courtyard, artificial playing surface or hot indoor workplace. Reassess conditions as the day changes, particularly when sunlight, wind, clothing or the amount of exertion changes. ¹⁶

The US National Weather Service’s HeatRisk forecast adds context by considering how unusual the heat is for a place and time of year, including daytime and nighttime conditions. Its colors run from green through yellow, orange and red to magenta as concern increases. People sensitive to heat may need precautions before the highest categories are reached. This makes it useful for planning errands, checking on relatives and deciding when a cooling alternative will be needed. Read the local explanation rather than treating the color as a universal safe or unsafe line for every person. An alert can guide preparation, but symptoms still determine the immediate response. Outside the United States, use the equivalent information from your local weather and public-health services. ¹⁷

Make the home cooler before symptoms appear

Some homes retain heat because they have little shade, limited ventilation or large sun-facing windows. Upper-floor rooms can be especially difficult to cool. UKHSA advises shading windows, reducing unnecessary indoor heat sources and opening windows when the outside air is cooler and it is safe to do so. Use the coolest suitable room and arrange access to an air-conditioned or otherwise cooler public place when needed. Consider travel safety and opening hours before relying on that option. A fan should not be treated as a guarantee of protection in an excessively hot room. This preventive advice is different from fanning wet skin during emergency cooling. Ask a landlord or housing service about persistent overheating, particularly when disability or illness limits the ability to leave. ²²

Neighborhood design can change heat exposure over short distances. Roads, roofs and buildings absorb and release heat, while areas with more vegetation and shade can be cooler. The EPA describes this as the heat-island effect, which can persist after sunset. A forecast for the wider area may therefore understate the conditions around a particular home, bus stop or walking route. When planning an outing, consider where shade and indoor rest are available along the way, not only at the destination. Communities can reduce exposure through trees, shade and changes to buildings and surfaces, but those improvements do not replace an immediate plan during a heat event. Limited access to cooling is a practical health issue, and people may need support arranging transport or finding an accessible location. ¹⁵

Hydration helps, but more is not always better

Make drinking water accessible during ordinary hot-weather activities and build regular opportunities to drink into the day. Carry a supply when leaving home and consider whether it can be refilled safely. Food containing water can contribute to daily intake, but a drink should be available rather than depending on food alone. Avoid making a fixed large-volume target the centerpiece of heat prevention. Needs differ with activity, weather and health, and some people have medical instructions about fluids. Ask the treating team how those instructions apply during hot weather. Hydration works alongside cooler surroundings, rest and suitable clothing; it does not remove the need for those measures. If someone develops emergency warning signs, stop treating the situation as a routine drinking problem and obtain urgent help. ^{24, 10}

Drinking far more fluid than the body loses can dilute blood sodium and cause exercise-associated hyponatremia. This is particularly relevant during prolonged exercise, and sports drinks do not eliminate the risk of overdrinking. The international consensus advises avoiding forced excessive intake and using thirst to help guide drinking in exercise settings. That principle should not be confused with a personalized plan for someone whose illness or medicines affect fluid needs. Headache, nausea, confusion and seizures can occur with hyponatremia as well as heat illness, so a bystander should not attempt to distinguish them by giving repeated large drinks. Emergency clinicians may need to check sodium and other findings. Tell them roughly what and how much the person drank during the activity, including unusually large amounts. ²¹

Workplaces need practical protection

A workplace heat plan should address the conditions that create exposure, not simply tell workers to be careful. The ILO describes heat as an occupational hazard affecting indoor and outdoor work. Prevention can involve reducing heat at its source, changing schedules or workload, providing suitable rest areas and ensuring that water and assistance are accessible. Workers and supervisors need a shared understanding of symptoms and a way to stop work and summon help. New starters and people returning after time away may need additional support. A plan is weak if breaks exist on paper but workers cannot use them in practice. Review what happened after a heat incident, including staffing, equipment and access to cooling, so that responsibility does not fall only on the person who became ill. ²³

Sport and group activities need decisions in advance

Sport-specific heat guidance can help organizers decide when to modify, shorten, postpone or stop activity. Sports Medicine Australia’s 2025 guidance considers the activity, clothing and environmental conditions rather than using one temperature for every sport. Appropriate changes can include longer or more frequent breaks, shade and active cooling, with suspension considered at extreme risk. These decisions should be agreed before participants are already struggling. Establish who has authority to change the session and how the decision reaches everyone. Gradual acclimatization is part of preparation, but it does not make a dangerous session safe or replace symptom monitoring. Coaches should account for equipment and the cumulative demands of repeated activity. Participants also need a clear route to report feeling unwell and leave the activity promptly. ¹⁸

Travel and unfamiliar climates

Travel can combine unfamiliar heat with an unusually ambitious activity schedule. A long walk, cycle ride or hike may be much more demanding after arrival from a cooler climate. The CDC Yellow Book advises reducing exercise intensity and duration during the first week when prior acclimatization is not possible. Fitness helps with activity but does not replace adjustment to the new conditions. Plan routes around shade, water and realistic exit options, and avoid packing the hottest hours with strenuous excursions. Carry the local emergency number and a way to describe your location. Tell companions about relevant health needs and agree that plans can change if someone becomes unwell. In remote areas, identify how help can be reached before starting rather than discovering a communication problem during an emergency. ¹⁹

Prepare a clear plan and handover

Write a short plan that someone else could use if you were unable to explain it. Include the emergency number, the location of a cooler place, a contact person and the information your care team has told you to keep available. For a group outing, assign responsibilities and confirm how everyone will find each other if plans change. Keep the plan brief enough to read quickly. After an incident, record the sequence of events while it is still fresh: when activity began, when a change was noticed, who called for help and what happened before responders arrived. Separate observations from assumptions. At follow-up, ask who will review outstanding results and what the next step is. A clear record makes it easier for the next person to understand the situation.

Frequently asked questions

Can someone with heat stroke still sweat?

Yes. Sweating can continue during heat stroke. Sweat or dry skin alone cannot confirm or exclude the diagnosis. ²⁸

Is cold-water immersion only for medical professionals?

No. First-aid guidance supports it when safe support and airway protection are possible. Call emergency services immediately. ⁴

Should I stop a medicine that increases heat sensitivity?

Do not change prescribed medicines yourself. Ask a clinician or pharmacist for an individual hot-weather plan. ⁹

What should I record after a heat emergency?

Record what you observed, when it happened, who called for help and what was done before responders arrived.