Heat Exhaustion vs. Heat Stroke: What’s the Difference?

The summer season offers perfect weather for outdoor activities with friends and family. However, if you're out in the sun for too long, your body may be unable to stay cool, leading to heat-related health problems. Heat stroke and heat exhaustion are common heat-related illnesses occurring from extended exposure to extreme heat. While both are considered a medical emergency, it's crucial to know the differences between the two so you know the signs when you or someone else is affected.

What is heat exhaustion?

Heat exhaustion is a heat-related illness that occurs when your body temperature gets too high and the body cannot cool itself properly. Being an older adult, working in a hot environment, and dehydration are big risk factors for heat exhaustion.

Heat exhaustion symptoms

Symptoms of heat exhaustion include the following:

Some of these symptoms of heat exhaustion require immediate medical attention to prevent fatal complications.

What is heat stroke?

If heat exhaustion is left untreated, it can progress to heat stroke, a severe heat-related illness. Heat stroke can also occur due to prolonged exposure to extreme heat and develops when the body temperature rises to 104ºF (40ºC) or higher. Older adults and young children are at higher risk for this condition, which is considered the most serious form of heat-related illness.

Heat stroke symptoms

Here are common signs and symptoms of heat stroke:

While heat exhaustion and heat stroke can share some symptoms, they also have distinct differences, with heat stroke presenting more severe and potentially life-threatening signs.

Heat exhaustion and heat stroke: what to do

While these heat-related illnesses share similar symptoms, they can require different forms of first aid to prevent further health complications. Below are the first aid instructions for tending to a person with heat exhaustion:

1. Move the person to a cool environment.
2. Loosen their clothing.
3. Apply cool, wet cloths or have the affected person sit in a bathtub of cool water.
4. Offer sips of cool water to lower their body temperature.

Heat stroke is a more serious heat-related illness that requires immediate emergency care. Here are the steps for rendering first aid to someone experiencing a heat stroke:

1. Call 911 immediately.
2. Move the affected person experiencing symptoms of heat stroke to a cool place out of extreme heat.
3. Remove any unnecessary clothing from the person's body and put them on their side to expose as much skin to the air as possible.
4. Cool down the person's body by immersing them in cold water or an ice bath.
5. If cold water immersion is not available, soak them with cold water from a hose or shower or apply wet, cold towels to as much of the skin as possible.

How to stay safe during hot weather

Below are tips for preventing heat exhaustion, heat stroke, heat cramps, and other heat-related illnesses.

Stay hydrated

Whether you're working outdoors or enjoying outdoor activities in extreme heat, make sure you're drinking enough water. Aim to drink one cup (or 8 ounces) of water every 15–20 minutes.

Use sunscreen

Using broad-spectrum sunscreen doesn't prevent heat-related illnesses, but it can prevent skin burns, which may reduce the risk of developing heat exhaustion or heat stroke. Sunscreens that provide the best protection from the sun have SPF values of 15 or higher. When using sunscreen, reapply it at least every two hours and more frequently if you have moist skin from excessive sweating or swimming.

Wear protective clothing

Wearing the right clothing can help prevent heat exhaustion and heat stroke. Regardless of whether you're working or relaxing in the summer heat, make sure your clothing is lightweight, loose-fitting, and made of breathable fabric. This type of clothing allows for proper airflow and the movement of air that can keep your body cool.

Take a look at the UV forecast

The National Oceanic and Atmospheric Administration (NOAA) predicts and tracks UV radiation levels in the Earth's atmosphere and forecasts the potential skin and eye damage this radiation may bring every day. Scores 0 to 5 indicate a low risk if you're exposed to the sun, while scores 6 or higher indicate that more damage can occur in a shorter period. This UV radiation index can help you plan outdoor activities in the hot weather to prevent sun overexposure.

Understand the heat index

The heat index, also known as the apparent temperature, is how hot it really is when relative humidity is combined with the actual air temperature. Prolonged exposure to heat indexes that are 103ºF (39ºC) or higher can lead to a higher risk of developing heat-related illnesses. Knowing the daily heat index can better prepare you for outdoor activities.

Bottom line

Both heat exhaustion and heat stroke are heat-related illnesses that can occur from prolonged exposure to extreme heat. While they share similar symptoms, like nausea, cramps, and elevated body temperatures, heat stroke can be a more serious heat-related illness that can become fatal quickly. If you notice someone experiencing one of these heat-related illnesses, administer first aid immediately and seek medical help.