Between soccer, swimming at the cottage and cycling around the neighbourhood, there’s no easier time of year than summer to stay active. And while it’s great to get outside, spending time in the sun on the hottest days of the year requires taking precautions — overheating and dehydration can pose a significant (or even fatal) threat to your health.

Fortunately, knowing the signs of heat-related illness and being prepared for the heat can help keep you and your family safe. Read on to learn how.

What is heat-related illness?

No matter what the temperature outside, our bodies strive to maintain an internal temperature of around 37oC, the temperature at which our cells and tissues can work the way they’re designed to. Deviate by a degree or 2, though, and your system will be under stress. Raise the temperature by 3 degrees and that stress will become life-threatening.

In the heat, we sweat to cool down, and the evaporating moisture draws warmth from our skin. However, sweating also means losing body fluids, as well as electrolytes (chemicals your body needs, like calcium, magnesium, potassium and sodium) and even small amounts of sugar. If you’re sweating profusely without replenishing fluids and electrolytes, you run the risk of disrupting your body's natural fluid balance.

When that balance is disrupted enough to affect your health, you end up with heat-related illness. The milder form of heat illness, called heat exhaustion, happens first. Left unaddressed, heat exhaustion may develop into heat stroke, which can be fatal.

Who is most at risk for heat illness?

Heat illness can affect anyone, but those most affected tend to include:

  • Children. In general, kids are more at risk than adults because they have a larger surface area compared to their body size, according to Dr. Dina Kulik, a pediatric emergency physician at The Hospital for Sick Children in Toronto. Also, babies and very young children can’t always ask for water or communicate when they feel uncomfortable, which can put them at a higher risk.
  • Older adults. As you age, it may be more difficult for your body to regulate your temperature, and those age 65 and older may not adapt as easily to a sudden increase in heat.
  • People with chronic health conditions. Health conditions like cardiovascular disease and some medications can make you more susceptible to heat-related illness.
  • Active people. Staying active in the heat means sweating more. You'll need to take greater precautions to prevent heat-related illness, especially if you already belong to another higher-risk group.

What are the early signs of heat-related illness?

Heat-related illness can creep up on you, since some of the earlier signs — like excessive sweating and thirst — may start out feeling only slightly more severe than the normal sweating or thirst you’d experience in warm weather. However, as it develops, heat exhaustion can also cause:

  • Muscle cramping
  • Dizziness, lightheadedness or disorientation
  • Nausea
  • Headaches
  • Feeling overheated, general discomfort

Left untreated, you can become more dehydrated, leading to the more serious symptoms of heat stroke, including:

  • Loss of consciousness
  • Rapid, strong pulse, or an abnormal heart rhythm
  • Seizures

In extreme cases, heat-related illness can even cause death.

Taking precautions can help you prevent heat-related illness

Preventing heat illness starts before you even go outside, through education and preparation. Know your (and your family’s) limits and be attuned to the signs of heat illness. Make sure you and your children are wearing hats, sunglasses and sunscreen, and drinking plenty of fluids, mainly water, recommends Kulik.

If you're at a higher risk for developing heat-related illness — for instance, if you belong to one of the groups listed above, or you're sweating heavily or playing vigorous sports — sip a hydration solution like Pedialyte or sports drinks throughout the day to help replace not just the fluid you’re losing, but also the electrolytes and sugar. (Watch your intake of sports drinks, though, as they contain more sugar than the average non-athlete needs.) Wear breathable and/or wicking fabrics, and make sure you and your family can easily get to cool shelter or shade.

If you or your child develop the early signs of heat illness like headache or nausea, get out of the heat and take (or offer) frequent sips of Pedialyte or a sports drink. Remove hot or restrictive clothing indoors, and apply a cool washcloth to your forehead or take a tepid bath to cool down.

If the symptoms continue or get worse, seek emergency medical attention.

Become a sun-safety role model

Simply becoming aware of the effects of heat-related illness and taking a few simple precautions can keep you and those around you safe. Check in on at-risk friends, relatives and neighbours during the hottest days of the year, and help your kids by becoming a role model for sun safety. That also means remembering sunscreen and protective clothing to protect yourself and your family from the sun’s burning rays as well as the heat.

“Kids are more likely to do what you do,” says Kulik. “If you show them positive behaviour, they will be more likely to emulate that.”