Some communities in Quebec are expected to get record-high temperatures and Environment Canada has issued several weather warnings and watches for heat.

Dr. Christopher Labos spoke to CTV News Montreal anchor Mutsumi Takahashi about heat and sunstroke and tips for preventing serious consequences in the sun.

Watch the full interview above.

MUTSUMI TAKAHASHI: What does it mean to get heatstroke or sunstroke?

DR. CHRISTOPHER LABOS: It basically means that your core body temperature has gone up. The official definition is your core body temperature has to get above 40.5 degrees Celsius, which is 105 degrees Fahrenheit. And that's because of the environmental heat, not because you have an infection or a fever, so it's not an internal source of increased heat.

It's the fact that it's so hot outside that your body loses the capacity to get rid of its excess heat, and so the core temperature goes up and starts to cause a series of problems.

TAKAHASHI: So what kind of symptoms would we feel then when that's happening?

LABOS: So at the beginning, you may not feel very much; you may just feel a little bit hot and flushed, your heart rate might go up, your blood pressure might go a little bit down, [and] you might become a little bit dehydrated.

But as it becomes more and more severe, you start to have more and more body systems get affected.

So as the dehydration gets worse and worse, your kidneys could shut down. As the temperature goes up, it starts to affect neurological function, so you start to become confused, at first, a little bit disoriented. And then that can progress into losing consciousness, seizures, [and] you could lapse into a coma and ultimately die.

Any organ system can be affected, and as the core temperature gets higher and higher, you start getting this syndrome of multi-organ failure that can lead to death. And frankly, the mortality rate to severe heat stroke is actually quite high when you start looking at everybody who presents at the hospital with this condition.

TAKAHASHI: So at what point then should we start to do something about how we're feeling? And also, if you see somebody else who appears to be getting some kind of a symptom? What do we do?

LABOS: You have to cool them off.

The treatment for this is to lower somebody's core temperature, and the best way to do that is to get out of the sun or to not get in the sun in the first place.

As the old joke goes, only mad dogs and Englishmen go out in the noonday sun.

The sun, especially when the humidity is high, can be dangerous. So when somebody's not feeling well, get them out of the sun, get them into a cool shaded area. If there's air conditioning, even better, get them water to fight the dehydration, and try to bring their core temperature down.

That's really what you have to do.

TAKAHASHI: And who is at higher risk for this?

LABOS: Anybody who's going to be exercising is going to be at higher risk.

Anybody who's not drinking water is going to be at higher risk people with pre-existing medical problems, like diabetes and cardiovascular disease, they are going to be higher risk.

Older individuals tend to be at higher risk as well for sort of a different set of reasons; they tend to live in older houses that may not have air conditioning. And as we get older, we tend to lose our thirst reflex a little bit, so they may not drink as much. So that puts them at higher risk for heatstroke because of those reasons.

TAKAHASHI: We've got a question from a viewer about exercising when it's a little warmer. She's a woman in her 60s. She says she does 40 minutes of fast walking every morning. But then she gets sluggish even when temperatures just go above 15 degrees. Her hands and feet get stiff, swollen. Is that something that is temperature related?

LABOS: It certainly could be.

Now here's the thing. As the as it gets hotter, and as it becomes more humid, that affects people with pre-existing lung problems.

Now, you may be fine in normal circumstances, but then all of a sudden, you get put into a situation of extreme heat and possibly extreme cold too, that can provoke sort of asthma-like symptoms. So you might be fine at baseline, but you only have a mild impairment at the extremes of temperature. So it is certainly possible. There are ways to sort of diagnose that, but this is not the first person to say that they have decreased exercise capacity when the weather starts to get either very, very hot or very, very cold. That is, unfortunately, a thing that happens.