As the midday sun intensifies, Busisiwe Khumalo is inside her homein Maitland, Cape Town.
Residents in the Western and Northern Cape have been warned of extreme heat and discomfort this week.
The extreme heat reminds Khumalo of a difficult period in December 2025, when her 12-year-old son suffered from heat stress due to outside temperatures soaring as high as 39 degrees Celsius.
“One day, he started sweating. His temperature was high. He also had a severe headache,” says the single mother.
“I went to the clinic, and the nurses told me it was because of the heat. He was given medicine for a headache, and he was advised to stay indoors to keep cool.”
According to the World Health Organisation, heat stress is the top cause of weather-related deaths globally, with almost 500 000 heat-related deaths annually.
Climate change causes heatwaves
Jennifer Fitchett, a professor of Geography in the School of Geography, Archaeology and Environmental Studies at the University of the Witwatersrand in Johannesburg, says that the 1.1 degrees Celsius post-industrial warming reported by the Intergovernmental Panel on Climate Change (IPCC) has increased the magnitude, severity and frequency of extreme climate events in Southern Africa.
Professor Caradee Wright, a lead of the Climate Change and Human Health Research Programme at the South African Medical Research Council, agrees. She says climate change is significantly increasing both the frequency and intensity of extreme heat in South Africa. This means that very hot days and heatwaves that were once rare now occur more often and last longer.
In 2024, people in South Africa were exposed to 13 heatwave days each, on average, according to a climate and health report from The Lancet. Of these, 10.5 would not have been expected to occur without climate change.
From 2012 to 2021, South Africa saw an estimated 4,500 heat-related deaths annually, 3 times as many as in 1990-1999, according to the report.
Experts say extreme heat is no longer just a weather issue; it is a growing public health threat.
Children and vulnerable populations most at risk
Children have a limited capacity to tolerate extreme heat compared with adults. Their bodies are still developing, and they are not yet well equipped to cool themselves,” explains Professor Lara Dugas, AXA chair in Non-Communicable Disease Epidemiology from Loyola University Chicago and hosted at the University of Cape Town.
“Adults have more surface area to allow for skin cooling, compared to small children with a limited amount of surface area to allow for cooling,” she says.
“This is especially important for infants and small children who cannot remove themselves from the hot environment if they are not fully mobile yet,” she says, citing an example of a small child in a car seat on a hot day, or strapped to their mother’s back.
Across the country, children, particularly from poor backgrounds, are exposed to heat because the schools and homes they live in are not designed to adapt to the changing climate.
Dugas says during heatwaves, children are prone to hyperthermia, heatstroke, and dehydration.
Vulnerable groups including the elderly, pregnant women, and those with pre-existing conditions such as hypertension, diabetes and mental illness are also at higher risk.
Dugas explains that extreme heat makes existing conditions worse by altering the immune system activity, making greater demands on the person’s ability to control their temperature, and may lead to more severe cases of dehydration.
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“Repeated bouts of dehydration may damage kidney function, leading to further hospitalisations and chronic kidney disease,” says Dugas.
“If someone is taking medication for an underlying or existing condition such as heart disease, the medications may negatively interact with a person’s ability to cool their body down, making the extreme heat even more unbearable.”
Heatwaves affect learning
Wright says extreme heat can substantially undermine children’s ability to learn, concentrate, and attend school. It affects both their physiology and their learning environments, with disproportionate impacts on children in poor communities.
“Exposure to high temperatures has been consistently associated with reduced attention, slower cognitive processing, impaired memory, and poorer test performance, particularly during prolonged heatwaves,” she says.
Fitchett explains that before extreme heat events are experienced, thermal discomfort occurs when a body feels too hot, which can result in concentration disruption.
“As we move closer to heat stress, the impacts on concentration are exacerbated, and outdoor activities, especially those such as sports which require exertion, pose a direct risk to health,” she says.
Heat-related learning impacts can exacerbate existing educational inequalities, particularly for younger children and learners in overcrowded or informal school settings.
Urgent climate change policy action is needed
In South Africa, temperatures have risen above global averages, placing growing pressure on health systems.
South Africa’s use of fossil fuels is worsening climate change, leading to increased heatwaves. Coal and oil make up most of the country’s energy mix. A report by the International Energy Agency (IEA) shows that 69.2% of South Africa’s energy supply is from coal, while 21.0% is from oil.
A sound climate policy reduces long-term health costs and safeguards population health. Children are the future of South Africa; protecting their health and allowing them to grow in a safe and healthy environment should be policymakers’ number one priority.
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