Heat Exhaustion vs Heatstroke: Symptoms, First Aid, Prevention, and When to Call for Emergency Help

Hot weather can be enjoyable, but prolonged exposure to high temperatures can quickly become dangerous. Whether you are spending time outdoors, exercising, working in the sun, or simply dealing with a heatwave, it is important to understand the warning signs of heat-related illnesses.

Heat exhaustion and heatstroke are two conditions caused by the body's inability to cool itself effectively. While heat exhaustion is usually treatable with prompt action, heatstroke is a life-threatening emergency that requires immediate medical attention.

This guide explains the differences between heat exhaustion and heatstroke, the symptoms to watch for, how to provide first aid, and practical tips to stay safe during periods of extreme heat.

What Is Heat Exhaustion?

Heat exhaustion occurs when your body overheats and struggles to regulate its internal temperature. It is often caused by prolonged exposure to hot weather, dehydration, or intense physical activity in high temperatures.

The condition can affect anyone, regardless of age or fitness level. However, certain groups are more vulnerable, including older adults, young children, people with chronic health conditions, and those taking medications that affect hydration or temperature regulation.

The good news is that heat exhaustion can usually be treated successfully if recognised early and managed quickly.

Common Symptoms of Heat Exhaustion

Symptoms can develop gradually over several hours or appear suddenly after physical activity in the heat.

Common signs include:

• Heavy sweating
• Feeling faint or dizzy
• Headache
• Weakness or tiredness
• Nausea or vomiting
• Loss of appetite
• Muscle cramps in the arms, legs, or abdomen
• Rapid heartbeat
• Fast breathing
• Body temperature of 38°C or higher
• Intense thirst
• Clammy or cool skin

Young children may not be able to describe how they feel. Instead, they may appear unusually sleepy, floppy, irritable, or less responsive than normal.

What Is Heatstroke?

Heatstroke is the most severe form of heat-related illness. It happens when the body's cooling system stops working properly, causing the core temperature to rise to dangerous levels.

Unlike heat exhaustion, heatstroke is a medical emergency. Without urgent treatment, it can damage the brain, heart, kidneys, and other vital organs.

Immediate emergency medical care can save lives.

Warning Signs of Heatstroke

Heatstroke may develop after untreated heat exhaustion or occur suddenly during extreme heat exposure.

Seek emergency medical help immediately if someone has:

• A body temperature of 40°C or higher
• Confusion or unusual behaviour
• Difficulty breathing or rapid breathing
• No sweating despite feeling extremely hot
• Hot, dry skin
• Seizures
• Loss of consciousness
• Unresponsiveness

If someone with suspected heat exhaustion does not improve after 30 minutes of cooling and hydration, treat the situation as a possible heatstroke emergency.

Heat Exhaustion vs Heatstroke: Key Differences

Although the two conditions are related, they require different levels of response.

Heat exhaustion usually includes heavy sweating, dizziness, muscle cramps, weakness, and dehydration. Most people recover after resting in a cool place and drinking fluids.

Heatstroke involves a dangerously high body temperature, changes in mental status, loss of consciousness, seizures, or an inability to cool down naturally. Emergency medical treatment is essential.

Knowing the difference can make a significant difference in preventing serious complications.

What to Do if Someone Has Heat Exhaustion

If you suspect someone has heat exhaustion, act quickly to help lower their body temperature.

Move them to a cool location. An air-conditioned room is ideal, but any shaded or cooler environment is better than remaining in direct sunlight.

Remove unnecessary clothing to allow heat to escape from the body.

Cool their skin using whatever is available. This may include:

• A cool wet towel or sponge
• Spraying cool water on the skin
• Applying cold packs to the neck and armpits
• Wrapping them in a cool damp sheet

Fan them while their skin is wet. The combination of moisture and airflow helps speed up evaporation, which cools the body more effectively.

Encourage them to drink water slowly. Oral rehydration solutions or sports drinks may also help replace lost fluids and electrolytes.

Remain with the person and monitor their condition carefully. Most people begin to feel noticeably better within 30 minutes if treatment is started promptly.

When to Call Emergency Services

Do not delay seeking emergency help if:

• Symptoms continue for more than 30 minutes despite cooling efforts
• The person becomes confused
• They stop sweating
• Their temperature reaches 40°C or above
• They have difficulty breathing
• They lose consciousness
• They experience a seizure

Call your local emergency services immediately if you suspect heatstroke. While waiting for medical professionals, continue cooling the person using water, cold packs, or damp towels if possible.

Who Is Most at Risk?

Although anyone can experience heat-related illness, some people face a greater risk.

Higher-risk groups include:

• Older adults
• Babies and young children
• People with heart disease
• Individuals with diabetes
• People living with kidney disease
• Those taking medications that affect hydration or body temperature
• Outdoor workers
• Athletes and people exercising in hot weather

Alcohol consumption and dehydration can also increase the likelihood of developing heat exhaustion.

Tips to Prevent Heat Exhaustion and Heatstroke

Prevention is always easier than treatment. During hot weather, simple precautions can significantly reduce your risk.

Stay well hydrated by drinking water regularly throughout the day.

Avoid strenuous physical activity during the hottest part of the afternoon.

Wear lightweight, loose-fitting clothing made from breathable fabrics.

Stay in shaded or air-conditioned areas whenever possible.

Use fans or cooling devices to improve airflow indoors.

Take regular breaks if working or exercising outside.

Never leave children, older adults, or pets inside parked vehicles, even for a few minutes.

Check on elderly relatives, neighbours, and anyone living alone during periods of extreme heat.

Applying sunscreen also helps protect your skin from sun damage, although it does not prevent heat-related illnesses.

Final Thoughts

Heat exhaustion and heatstroke are serious conditions that become more common during periods of extreme heat. Recognising the early warning signs and responding quickly can prevent a medical emergency.

If someone develops symptoms of heat exhaustion, move them to a cool place, help lower their body temperature, and encourage them to drink fluids. If they fail to improve within 30 minutes or show signs of heatstroke, seek emergency medical help without delay.

As temperatures continue to rise during summer months, staying informed and prepared can help protect you, your family, and your community from the dangers of overheating.

Source: BBC News (updated 22 June 2026) and advice from UK health authorities.

Disclaimer: This article is for general educational purposes only and should not be considered medical advice. If you suspect someone has heatstroke or is experiencing a medical emergency, contact your local emergency services immediately. Always seek advice from a qualified healthcare professional regarding medical concerns.