Heat stroke vs. heat exhaustion: How to tell the difference

Living in Texas, you’re likely very familiar with the intense triple-digit heat we experience in the summer months. But just because it’s hot outside doesn’t mean you are spending the entire day inside; outdoor activities still go on. Maybe you’re cheering at a Saturday morning soccer tournament, pushing through a long run or finishing out yard work that needs to be done.

Something starts to feel off and your head starts pounding, you feel a little dizzy and you're not sure if you should sit down and drink some water or go to the emergency room.

That moment of uncertainty is exactly why understanding the difference between heat stroke vs. heat exhaustion is so important. These are two very different conditions that are often confused. Knowing which one you are experiencing could be the most important call you make all summer. 

Who is at risk of heat stroke vs. heat exhaustion

Heat-related illnesses are becoming more common year after year. According to the Centers for Disease Control (CDC) Heat & Health Tracker, emergency departments nationwide saw approximately 119,000 visits for heat-related conditions back in 2023, which was the highest annual total reported since the tracking system began. Texas accounted for one of the largest shares of those visits, ranking second among all states.

Both heat exhaustion and heat stroke happen when your body loses its ability to manage rising internal temperature. In Texas, summer outdoor temperatures regularly push past 100°F and the humidity in many parts of the state makes it harder for sweat to cool you down the way it is supposed to. 

Your body is working overtime trying to keep your core temperature in a safe range, and when it starts losing that fight, heat-related illness can follow. Heat exhaustion comes first. If you ignore it and keep pushing, it can progress into heat stroke, which is considered a medical emergency.

Anyone spending time outdoors during a Texas summer can feel the effects of extreme heat, but some groups face a much higher risk of developing heat exhaustion or heat stroke, such as:

• Athletes training outdoors during summer months
• Construction workers and landscapers
• Hikers and campers in areas without shade
• People who work in their yards during the hottest parts of the day

Children and older adults are also more vulnerable because their bodies are less efficient at regulating temperature. Also, certain medications can reduce your body's ability to respond to heat, including diuretics, antihistamines, and some blood pressure medications.

What are the first signs of heat exhaustion?

Heat exhaustion is your body sending a warning sign when the heat begins to be too much. It's not subtle, but it is manageable if you catch it and respond right away. The key is recognizing the heat exhaustion signs early, because your body is still working hard to cool itself down.

Common signs of heat exhaustion include:

• Heavy sweating
• Cool, pale or clammy skin
• Fast but weak pulse
• Nausea or vomiting
• Muscle cramps, especially in the legs or abdomen
• Tiredness and weakness
• Dizziness
• Headache
• Fainting or feeling like you might faint

If you notice these signs of heat exhaustion in yourself or someone with you, the situation is serious but treatable outside of a hospital in most cases. Your body is asking you to do three things:

1. Stop
2. Cool down
3. Rehydrate

When heat exhaustion turns into heat stroke

Heat stroke is an entirely different condition from heat exhaustion. This is when the body's internal temperature climbs to 104°F or higher, and your internal cooling system shuts down. At this point, your organs are at risk, including your brain. Heat stroke requires immediate emergency medical care, and every minute counts.

One of the most important things to understand about heat stroke is that your sweating may actually stop. While heat exhaustion produces heavy, drenching sweat, heat stroke can leave the skin hot and dry. That shift is a major warning sign that your body is no longer able to regulate itself through sweating.

Signs of heat stroke include:

• High body temperature (104°F or higher)
• Hot, red skin that may be dry or damp
• Rapid, bounding pulse
• Confusion, slurred speech or disorientation
• Loss of consciousness
• Seizures
• Nausea or vomiting
• Throbbing headache
• No longer sweating despite the heat

If you or someone you’re with is confused, unconscious or no longer sweating, call 911 right away. Do not wait to see if they feel better with rest and water. Heat stroke can cause permanent organ damage or in some cases, even death if not treated quickly.

Heat exhaustion vs heat stroke: A quick comparison

Find the right care you need with our symptom checker

Treat for the heat: When heat illness becomes an emergency

A national study regarding emergency room visits for heat illness found that 74.7% of cases were heat exhaustion and only 5.4% were heat stroke. If you believe someone has heat exhaustion, it’s important to move quickly but stay calm.

• Get out of the heat and move to an air-conditioned space or shaded area
• Loosen or remove extra clothing
• Cool the body down with cool (not ice-cold) water, a cool wet cloth on the neck, armpits and groin, or a fan
• Drink cool water or a sports drink if you or the person is awake and able to swallow
• Lie down and elevate your feet slightly

Most people with heat exhaustion begin to feel better within 30 to 60 minutes of cooling down and rehydrating. If symptoms are not improving within that window, or if they get worse at any point, call 911 or go to the emergency room.

If you suspect heat stroke, the steps are simpler because there is really only one, which is to call 911 right away. While you're waiting for help to arrive, begin cooling the person as aggressively as you can. 

• Apply ice packs to the neck, armpits and groin
• Pour cool water over the body
• Use a fan to increase airflow
• Do not give fluids by mouth if the person is confused or unconscious

Hydration is the foundation for preventing heat-related illness

Most heat-related illnesses start with dehydration. By the time you feel thirsty, you're already behind. In the summer, especially if you're active, you need to be drinking water continuously, not just when your mouth feels dry. A general rule for if you are working or playing outdoors in the heat is to aim for about 8 oz of water every 15 - 20 minutes.

For short sessions in the heat, water works well. Longer sessions can benefit from sports drinks, which can help replace electrolytes lost through heavy sweating. This is particularly relevant for athletes and people doing prolonged physical work. Avoid alcohol and drinks with caffeine during periods of heavy activity in the heat, as both can speed up dehydration.

One often-overlooked factor in hydration is the color of your urine. Pale yellow is a healthy sign. Dark yellow or amber means you need more fluids. If it looks more like the color of apple juice, stop what you're doing and drink water steadily over the next hour.

Related: Hydration hacks: Fun, innovative ways to boost your water intake

When it comes to the heat, trust what your body is telling you

One of the more challenging things about heat exhaustion and heat stroke is that they can sneak up on you, especially when you're focused on a goal such as finishing a run or not wanting to leave a game early. Texas summers have a way of making people push past the signals their body is sending.

If something feels off, like dizziness, nausea, a sudden wave of weakness or a headache that came out of nowhere, those are your body's early warning system doing exactly what it's designed to do. Responding to those signals early means you can usually manage things yourself. Pushing through them can turn a manageable situation into an emergency. 

Even if you've cooled down and your symptoms have improved, it's worth a conversation with your doctor if you experienced significant heat exhaustion or symptoms suggesting heat stroke. They can check for dehydration, assess your recovery and help you understand if there are any underlying factors that make you more vulnerable.

Looking for more ways to beat the heat? Subscribe to the Scrubbing In newsletter for more helpful and timely wellness advice.