What’s the difference between heat stroke and heat exhaustion?

Paying close attention to heat advisories in your area during the hot summer months can be life-saving, because some outdoor activities can become dangerous.

If you plan on being outdoors, and especially if you’re planning on being active, it’s important to know the signs of heat-related illnesses like heatstroke and heat exhaustion. Both conditions occur when the body becomes dehydrated in hot or humid environments, but the combinations of symptoms differ between the two. If you think someone has heatstroke, immediately call 911 or seek emergency care.


Symptoms of heat exhaustion

Heat exhaustion happens when the body is overheated, usually with a fever of up to 104 degrees Fahrenheit. One of the differences in symptoms between heat exhaustion and heatstroke is sweat; heat exhaustion is characterized by heavy sweating, while those suffering from heatstroke experience decreased sweating. Other symptoms of heat exhaustion may include:

  • Agitation
  • Cool and clammy skin
  • Confusion or anxiety
  • Dizziness
  • Excessive thirst
  • Fainting
  • Headache
  • Muscle aches and cramps
  • Nausea
  • Slow heartbeat
  • Weakness and fatigue

Symptoms of heatstroke

Heatstroke occurs when the body’s temperature rises so much that the cooling system stops working altogether. This typically happens at body temperatures of 104 - 106 degrees Fahrenheit, but keep in mind that it can occur suddenly. It is possible for your body to overheat so quickly that it skips past the symptoms of heat exhaustion and goes straight to heatstroke. Heatstroke is very serious and is a medical emergency.

As mentioned above, heatstroke is characterized by decreased sweating, as well as hot, flushed skin. Other symptoms include:

  • Confusion, delirium or loss of consciousness
  • Convulsions
  • Decreased urination and/or blood in urine or stool
  • Dizziness or vertigo
  • Fatigue
  • Headache
  • Nausea and vomiting
  • Rapid heart rate
  • Shortness of breath

Heat illnesses can be very serious and potentially life-threatening. Both heatstroke and heat exhaustion may have similar symptoms, and by understanding the symptoms, you can get the right care for yourself and loved ones.


If you are experiencing a life-threatening emergency, go directly to the ER or dial 911.