Warning Signs of Heat Illness

Keep an eye out for heat illnesses at the Marathon this weekend. Even as a spectator, you could save someone’s life.
Heat illness is common with heavy physical activity, and incidence increases in hot or humid temperatures. The Chicago Marathon this weekend is shaping up to be a prime candidate for heat illness, with temperatures predicted to soar to 77 degrees. With temperatures being cool for many weeks recently, athletes may not be acclimatized to such warm weather, increasing chances of dehydration and worse. The good thing is that with proper hydration and conscious monitoring of symptoms, heat stroke in athletes is entirely preventable. This blog is meant to alert you to the signs and symptoms of heat illness in yourself, fellow runners, and for spectators who may witness heat-related crises.
Heat related illness should be though of as a spectrum that works though the phases — from dehydration all the way to heat stroke. It’s important to remember that any heat illness is a warning sign and should be addressed.


Dehydration is inadequate fluid in body tissue, and is a basic component of all heat-related illnesses. While dehydration is a less serious form of heat illness, you will notice that the warning signs of dehydration are similar to the more severe heat illnesses and that the severity of symptoms progresses as the illness becomes worse. This can happen very quickly. Do not take dehydration lightly.

Warning signs of dehydration:

  • Fatigue or weakness, headache, dizziness, feeling irritable
  • Nausea
  • Excessively thirsty, feeling of dry mouth

Worsening signs can indicate decline into more severe stages and include:

  • Disorientation/delirium
  • No appetite/not thirsty
  • Lowered BP or rapid pulse
  • Tenting of skin: if you pinch the skin on the back of the hand, it will stay like that
  • Decreased sweating
  • Unconsciousness

Care for dehydration:

  • Replace fluid by drinking small sips of carbohydrate/electrolye fluid such as sports drink, milk, juice, water. Patients may require an IV if severe/unconscious


Heat cramps are painful involuntary muscle spasms that occur from exertion in high heat/high humidity conditions do to lack of fluids. They often appear in the legs or abdomen, but can occur other places. Heat cramps are an early stage of heat illness.

How to reduce cramps:

  • Rest
  • Gently massage and lightly stretch the cramped muscles
  • Consume small sips of carbohydrate/electrolye fluid such as sports drink, milk, juice, water
  • Resume activity with caution if the cramps resolve
  • Take frequent breaks and continue hydrating to prevent further cramping


Heat exhaustion results when fluid loss through perspiration is not replaced.
Heat exhaustion is a more severe form of heat-related illness. Body temperatures begin to rise between 98.6°F-104°F. People with heat exhaustion usually are aware, appropriately oriented and can talk to you.


  • Cool, moist skin — can be pale ashen or flushed
  • Extremely heavy sweating
  • Weak, dizzy, lightheaded, headache —> progressing to exhaustion, decreasing consciousness. Confusion is a bad sign that things are going south
  • Nausea and vomiting
  • Muscle cramps
  • Rapid weak pulse, low blood pressure, shallow breathing

 What to do:

  • Move to a cooler area, in the shade or inside
  • Apply cool wet cloths/towels to the skin
  • Apply ice packs/cold pack wrapped in a thin towel to wrists, ankles, armpits, groin, and back of neck — large blood vessels are superficial here
  • Call EMS if patient does not improve in a few minutes, will not drink water, starts vomiting, loses consciousness, or passes out

**People with heat exhaustion can progress very quickly to heat stroke. Ideally, the athlete or patient should get into a baby pool with ice water


Heat stroke is the most serious heat related illness. This is a life-threatening condition where the body temperature can quickly soar over 104 degrees. There are two types: Classic, which develops slowly due to environment and weather like a heat wave and Exertional, due to internal production of heat through exercise which exceedings body’s ability to cool off. This develops quickly and is often seen in sporting, exercise or strenuous labor in all weather conditions. A person with heat exhaustion is often confused, disoriented, and losing consciousness.

Signs of Heat Stroke:

  • Flushed/red, dry skin. May be no longer sweating in heat wave scenarios, but with exertional heat stroke like running in hot weather, they may be sweating profusely
  • Extremely high body temperature
  • Rapid weak pulse, shallow breathing, low blood pressure
  • Throbbing headache
  • Dizziness with nausea and vomiting
  • Decreasing level of consciousness: patient may be confused, disoriented, hysterical,unable to pay attention, acting irrationally
  • Unconsiousness/coma
  • Staggering/convulsions/siezure

 If you suspect someone has heat stroke:

  • This is a life-threatening condition. Immediately call 911/EMS
  • Ideally submerge the patient in an ice bath or trash can filled with ice water
  • Begin rapid cooling: Spray them continuously with cool water, douse patient with ice-water soaked towels over the whole body, place them near a fan, cover them with ice towels or bags of ice placed all over the body. Keep the cold wet towels rotating and cold
  • Monitor for/try to minimize shock, make sure the patient is breathing
  • Be prepared to give CPR if necessary

References: American Red Cross/Evidence in Motion Emergency Medical Response for the Sports Venue (2015); NATA Position Statement on Exertional Heat
Illnesses; AJSM/AOSSM Heat-Related Illness in Athletes