As southern Ontario and Quebec swelter through yet another heat wave, public health experts are warning of the dangers of not staying cool.

Children, seniors and those with chronic breathing issues are at particular risk when temperatures soar into the 30s and the humidex rises to the low 40s.

The danger on days like these is that the air temperature can rise above normal body temperature – about 37 Celsius. That's when the body begins having trouble transfering heat out of the skin into the air. It becomes even more difficult when there's plenty of humidity in the air.

On days of sticky heat and humidity, it doesn't take long for heat-related illnesses to crop up, such as heat cramps, heat rash and the most dangerous of them all, heat exhaustion and heat stroke.

Heat stroke is a true medical emergency. It occurs when the body's temperature rises above 41 degrees Celsius and can result in permanent brain damage or death if not treated quickly. Symptoms include:

  • a rapid pulse that gets weaker and harder to feel in later stages
  • hot and dry skin, as the body shuts down sweating
  • noisy breathing
  • flushed skin
  • severe headache
  • fainting
  • confusion or dizziness
  • nausea, vomiting
  • convulsions and eventually, unconsciousness.

If heatstroke is suspected, call 911. It is critical that the body temperature be lowered as quickly as possible. While waiting for help, sponge the victim down with cool, not cold, water, particularly in the armpits and neck

To prevent heat-related illnesses, here are a few tips:

  • Avoid being outdoors during the hottest part of the day, which is typically the afternoon
  • Try to spend the day in air conditioned places such as shopping malls, libraries, or public pools
  • Drink plenty of cool fluids, like water, even if you don't feel thirsty
  • Avoid caffeine and alcohol
  • Avoid outside activities requiring exertion
  • Work and exercise in brief periods and take frequent breaks
  • Dress in light, loose clothing and wear a hat
  • Take a cool bath or shower periodically or cool down with cool, wet towels