The sun’s shining and it’s gorgeous, so it’s no wonder many of us, including personal trainers, are taking advantage of the summer weather by exercising outside. But beware: the heat can be a killer. Seriously.

The main cause of heat exhaustion and heat stroke (aka sun stroke) is insufficient fluid intake while working out or performing strenuous physical activity. Fluid intake is essential to assist in healthy bodily functions as well as produce sweat, which helps cool down the body. However, if you don’t drink enough, the body will use liquids to satisfy bodily function requirements first – which is the problem. Since you won’t sweat, your body won’t be able to cool down, allowing the core temperature to rise to a level that could kill your cells, damage your brain and cause serious health problems.

Heat exhaustion is a sign that your body is unsuccessfully cooling itself down. You’ll look pale and feel clammy. You’ll also most likely feel faint, nauseous, weak, lightheaded and have a headache. Muscle cramps may develop, and you’ll be sweating profusely. To treat heat exhaustion, all you have to do is cool yourself down. Remove clothing, move to a cooler area, and drink some water or something with electrolytes and a bit of sugar (e.g. Gatorade). Don’t gulp – just drink a bit at a time.

If you’re breathing is shallow and you’re not sweating, have a headache, rapid pulse, hot red skin, and are acting strangely, then you’ve got heat stroke. Heat stroke is far more serious because your insides are basically “cooking” due to the rising core temperature. Needless to say, this requires immediate medical attention. Move to a shady spot, wrap yourself up in cool, wet towels, drink water or a sports drink, and get medical treatment from a professional.

Beat the heat by drinking plenty of water before you even think about working out. It’s a good habit, especially for the summer. Health Canada recommends drinking 2 to 5 cups of water at least 3 hours before you workout, and about a cup every 20 minutes while working out. Wear clothing suitable for hot weather, sticking to loose fitting items that are light in colour.

And because humidity makes it harder for the body to cool itself down, since sweat won’t evaporate as easily, you may want to consider moving your workout indoors or waiting until the humidity isn’t so high.