Canada and United States are suffering from a strong heat wave. At least 233 sudden death notices have been filed in recent days in the Canadian province of British Columbia. The city of Lytton broke for the 3rd day in a row the record for highest temperature already registered in the country: 49,5ºC. With that, the question remains: how can extreme heat affect the human body?

O Olhar Digital he spoke with physician Jamiro Wanderley, from Unicamp, in São Paulo. The specialist explained what can lead to the death of people exposed to a sudden high heat and how to avoid further damage in these situations.


According to the doctor, the human body has a good capacity to adapt, both at high temperatures, such as in deserts, and at lower temperatures, such as the poles. However, a sudden change in people who are not used to it can lead to more severe problems.

“In this hot situation, the main symptom is dehydration. The body starts to sweat more and needs more fluid. In this case, those who suffer most are the extremes of age. Both the older ones, who sometimes cannot pick up water frequently, and the younger ones, who are small and have little water in their bodies,” said Wanderley.

Symptoms of dehydration include constant thirst, little urine, lack of sweat, dry skin and lips. In severe cases it can lead to a reduced heartbeat and even a low-grade fever. To avoid pictures like this, it is necessary to replace liquid, both with water and isotonic drinks.

In addition to dehydration, excessive heat can make it difficult for enzymes in the human body to function. This picture can lead to a piece of cake and even fainting. This can even result in low pressure. Care needs to be redoubled also with people with heart disease, due to the low heart rate that high temperatures can cause.

"To avoid this, it is important to be careful not to be exposed to heat, drink plenty of fluids, keep the place ventilated and keep an eye on the symptoms", concludes the doctor.

Extreme heat wave can become recurrent

Last Tuesday (29), thermometers in Portland, Oregon, reached an impressive 46°C, the highest temperature recorded at the site since measurements began in 1940. Average temperatures for this time of year in Oregon are typically around 23°C.

According to Science News, the heat was so extreme that it melted power cables from Portland streetcars and caused asphalt and concrete roads in western Washington to expand and crack.

These high temperatures are particularly dangerous in a region that is normally cold, unaccustomed or unprepared for it, increasing the risk of heat-related deaths and other health hazards. Ground-level ozone levels, for example, reached the highest ever seen in 2021, and the chemical reactions that form the gas were amplified by a potent mixture of high heat and strong UV light.

British meteorologist Scott Duncan has made a series of Twitter posts about the unusual heat and jet pattern that created that heat dome over the Pacific Northwest.

Read more:

“Historical records indicate that similar patterns of high pressure have brought heat waves to the region,” says O'Neill. But, this one is different. "A typical severe heat wave in the past could lead to temperatures of around 37,7°C, not 46°C."

The US is going through a historic drought. Almost half of the country faces the worst drought in 20 years, called a 'megadry' by the American press. The data are from a balance of the country's Drought Monitor released on Tuesday (29). It is a federal information system created to monitor this climatic episode. Water scarcity and the risk of fires already affect 11 states.

All of this represents many dangers for the planet, especially for human health. In May, scientists reported in Nature Climate Change that 37% of heat-related deaths between 1991 and 2018 were attributed to man-made climate change.

“When we talk about climate change, the conversation is often a little more abstract,” says O'Neill. "We are experiencing this in practice now."

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