Every summer when extreme heat arrives in Dhakale, India, Pramila Waghmare notices her children’s grades drop, only to improve again when winter arrives. After three years of this pattern, she asked her neighbours and learned that heat waves seemed to be hurting the academic performance of at least 40 schoolchildren in her hamlet with a total population of less than 1,000.

Schoolteachers told her that students in many nearby villages in Maharashtra state had similar problems, especially a loss of focus and a sharp decline in math performance.

“During the summer, I can’t concentrate,” said Waghmare’s 9-year-old daughter Kavya. “My friends and I feel like running away and sitting in the shade of the mango tree.”

By this past April, it was already difficult for students to focus as temperatures in the village exceeded 36°C. Teachers told Waghmare that during peak summer heat, most students stop participating actively by the afternoon.

Relatives from nearby villages and teachers and community health care workers across India have also noticed more days of extreme heat that make children listless, struggling to remember what they have learned and taking longer to respond to questions. It’s not just India: Extreme heat is making it harder for students to learn in classrooms around the world.

After decades of global warming and worsening heat waves, the physical effects of extreme heat are well known: dizziness, fainting, sleep disruption, labored breathing, and sometimes heat exhaustion. Large-scale studies are now revealing to scientists precisely how children’s brains and cognitive skills are suffering, making it harder to learn, concentrate, and perform. Experts say it is important for teachers to be understanding and for children to drink a lot of water and avoid physical exertion until the weather cools.

But with extreme heat getting worse and affecting millions of people a year, the problem is too big for teachers to tackle on their own. Systemic change could help. For instance, school administrators could stop planning tests for hot summer months and create areas for teachers and students to cool off on extremely hot days.

Numbers Don’t Lie

An analysis by Save the Children showed that from July 2023 to June 2024, 766 million children, or one-third of the world’s children, faced extreme heat waves – double the previous year’s number. During that period, the report also indicated that 344 million children experienced the highest temperature recorded in their area since 1980.

Studies show extreme heat makes it harder to perform cognitive tasks, such as math, that require attention, memory, and problem-solving. One study from China found that even short-term exposure to high temperatures hurt math scores. Researchers tracked eight years of test scores and matched them with the exact weather on test days. At temperatures above 32°C, math scores dropped noticeably compared to moderate days of 22-24°C.

Xi Chen, an associate professor of health policy and economics at the Yale School of Public Health and one of the study’s authors, said dehydration may impair children’s short-term memory, attention, and psychomotor skills used in writing, drawing, and other tasks that involve both thinking and movement.

“It also disrupts electrolyte balance, which is essential for neural signaling. This is particularly important in tasks like arithmetic, which depend on working memory and concentration,” he explained. Chen noted that children’s bodies are less efficient at regulating body heat, causing them to overheat more quickly than adults during heat waves. It is harder for children’s core body temperatures to stay in the healthy range of between 36.5°C and 37.5°C.

During extreme heat, “cerebral blood flow may be reduced, leading to less oxygen and nutrient delivery to the brain,” he said. Consequently, the brain activates protective mechanisms that reduce overall activity to conserve energy and avoid damage. This stress can impair performance in tasks requiring sustained attention, working memory, and executive function.

In the United States, a study of 11,000 children linked extreme heat to lower performance across various learning tasks. Extreme heat is also more likely to affect Black and low-income and economically disadvantaged neighborhoods. As many teachers in the U.S. know, schools in poorer communities are much less likely to have air-conditioned classrooms. Globally, one study estimates that in low- and middle-income countries, up to 4 billion people may lack access to air conditioning by 2050. 

One Chinese study involving nearly 180,000 children found that increased heat exposure was linked to a higher risk of attention-deficit hyperactivity disorder, or ADHD. In another study, scientistsfound that preadolescents exposed to higher ambient temperatures for just one week exhibited weakened communication within key brain areas, including the salience network, which regulates attention, emotion, and mental health. Lead author Dr. Laura Granés said poorer sleep quality during hot nights also helps explain how extreme heat can alter brain connectivity in children.

“Sleep deprivation can, in turn, lead to changes in brain connectivity,” said Granés, a postdoctoral researcher at the Primary Health Care University Research Institute Jordi Gol, Spain. Poor sleep can impair the ability of the brain’s prefrontal cortex to consolidate memories, focus attention, and execute effective problem-solving and decision-making.

She said high temperatures also can activate the hypothalamic-pituitary-adrenal axis, a key stress-response system in the body. Increasing levels of the stress hormone cortisol can exacerbate health problems and disrupt how different parts of the brain communicate with each other.

When Classrooms Turn Into Ovens

In Maharashtra’s Bhadole village, 11-year-old Sarthak Sonawane struggles to remember what he learns in school during summer.

“He just wants to run away from school,” says his mother, Sangita Sonawane. The only fan in his classroom seldom works because of frequent power outages, and the extreme heat makes him eager to leave his school and go home.

“He just wants to swim in a well the entire day,” his mother said. Over the past four years, Sarthak has gradually lost interest in school and now wants to drop out. “With no solution to this extreme heat, I constantly worry about his future,” his mother added. “Public schools in our villages lack even the most basic resources. What can the teachers do?”

One step could be to stop conducting exams during months of sweltering heat, as is the practice now.

“Schools need to adapt to extreme heat and design their policies considering how heat affects children,” she said. The same holds for Europe, where many children still attend school during summer months even as the continent endures more frequent and longer spells of extreme heat.

Granés noted that “in southern European countries, school calendars are often adjusted to avoid the hottest period, but similar adaptations may soon be needed more widely as extreme heat becomes increasingly common across the continent.”

Some European cities have already begun converting schools and public spaces into climate shelters, a move that could create safe environments where children spend most of their time, she added. Cities like Barcelona have redesigned schoolyards and public buildings as part of the climate shelters network to provide cool, safe havens during heat waves. Starting with 20 such shelters in 2020, the number has grown to nearly 400 shelters this summer, ensuring that 98% of the population lives within a 10-minute walk of a shelter and 68% within a five-minute walk. 

Additionally, Granés recommends raising awareness among families, caregivers, and educators about the risks of heat exposure.

“Children should be encouraged to drink water regularly, especially if they are playing or exercising outdoors,” she said. Preventive measures, such as scheduling outdoor activities during cooler hours, ensuring access to shaded areas, and maintaining well-ventilated indoor spaces, can make a big difference, she said. 

In Waghmare’s village, teachers now encourage students to study more at home in the evenings when temperatures are slightly cooler. However, her house has a tin roof, which absorbs heat and radiates it indoors, making it unbearably hot inside.

Waghmare said she feels helpless: “Never in my life did I imagine that someday these rising temperatures would affect education and prevent children from going to school.”