Extreme Heat May Be Damaging Young Children’s Brains, Study Finds

As the planet’s temperatures increase, will grades and IQs plummet?

The world may be raising a generation of children whose early learning could face lasting setbacks, and the culprit isn’t inadequate schools or malnutrition alone. It’s heat.

A sweeping analysis of nearly 20,000 young children across six countries has revealed that toddlers growing up in areas where temperatures regularly exceed 32°C are falling significantly behind their peers in foundational skills like counting, letter recognition, and basic problem-solving. As the planet barrels toward its warmest years on record, the research raises urgent questions about whether rising temperatures could leave lasting marks on cognitive development.

The 32-Degree Threshold

Jorge Cuartas, a researcher at New York University who led the study, noted the research reveals effects on foundational learning abilities. The analysis examined children aged three and four in Georgia, The Gambia, Madagascar, Malawi, Sierra Leone, and the State of Palestine, matching each child’s location and birthdate to detailed temperature records spanning their short lives.

The study, published in the Journal of Child Psychology and Psychiatry, revealed that children exposed to average maximum temperatures above 32°C during their early years scored substantially lower on developmental assessments compared to those raised in cooler conditions. After accounting for wealth, maternal education, baseline climate patterns, and geographic factors, the researchers found that kids experiencing sustained heat were between 1.8 and 7.7 percentage points less likely to be meeting basic developmental milestones.

The year 2024 shattered temperature records, marking the first time annual average temperatures exceeded 1.5°C above pre-industrial levels. Current policies place the world on track for warming between 2.1 and 3.9 degrees Celsius, according to climate projections. For young children whose brains are constructing the neural architecture that will support decades of learning and decision-making, this trajectory raises serious concerns.

Poor Families Hit Hardest

Heat doesn’t appear to affect all children equally. Poor families shoulder the heaviest burden. While children from wealthier households showed some ability to weather high temperatures, those from families below the median wealth level were significantly less likely to be developmentally on track. The gap reveals how climate change functions as a multiplier of existing inequalities, punishing those with the fewest resources to adapt.

Access to clean water emerged as a critical buffer. Children in households lacking improved sanitation faced steeper declines in their development scores during periods of high heat. Water offers not just hydration but a means of cooling, both for drinking and washing, that becomes essential when temperatures climb.

Children in cities showed much larger declines than their rural counterparts. Urban children exposed to extreme heat showed developmental scores 22 to 27 percentage points lower than expected. Rural children, by contrast, didn’t exhibit the same dramatic pattern. The difference likely stems from the urban heat island effect, where concrete and asphalt trap warmth, pushing temperatures several degrees higher than in surrounding countryside. More children worldwide now grow up in cities than ever before, meaning this urban penalty affects an expanding population.

Math and Reading Skills Take the Biggest Hit

The cognitive toll appeared most severe in early math and literacy skills. Children struggled more with recognizing shapes, understanding basic number concepts, and identifying letters when raised in hot conditions. Physical development and social-emotional growth showed less consistent associations, though the researchers noted their measurement tools for these domains had limitations.

Young children face a biological disadvantage when temperatures soar. Their sweating response hasn’t fully matured, making it harder for their bodies to release heat. Sustained exposure to high temperatures can trigger dehydration, disrupt sleep patterns, cause inflammation in developing nervous systems, and activate stress hormones that interfere with normal brain maturation.

The effects ripple through families and communities. Parents dealing with their own heat-related stress may have less patience or energy for engaged interactions with their children. High temperatures damage crops and increase food contamination risks, threatening the nutrition young brains require. Mosquitoes carrying diseases like malaria thrive in warmer conditions, creating additional health hazards.

Heat also constrains children’s worlds. When outdoor temperatures become unsafe, toddlers spend less time playing outside, exploring their environment, and engaging with other children—all activities that build cognitive and social skills during critical developmental windows.

How Researchers Measured the Effects

The research team used the Early Childhood Development Index, which measures whether kids can perform age-appropriate tasks across four domains: physical health, social and emotional skills, approaches to learning, and literacy and numeracy. By matching geographic coordinates from household surveys to high-resolution climate data, the researchers calculated the average maximum monthly temperature each child experienced from birth through their assessment date.

A crucial finding: the 32°C threshold. Below this temperature, children’s development showed little association with heat exposure. Above it, outcomes declined. This threshold matters because it falls within the range already experienced by millions of children today, and climate projections suggest many more regions will regularly exceed this mark in coming decades.

The study’s geographic scope strengthened its conclusions. By examining children across different continents, climates, and economic systems—from the Mediterranean weather of the State of Palestine to Madagascar’s tropical heat to Georgia’s temperate zones—the researchers demonstrated that the temperature-development link wasn’t specific to one culture or region.

Some limitations temper the findings. The analysis couldn’t track families who moved, potentially missing children who relocated to escape heat or pursue opportunities. The temperature measurements represented monthly averages rather than capturing extreme heat waves that might have even stronger effects. Parent-reported developmental assessments, while widely used, have less precision than direct testing, particularly for social-emotional skills.

Still, the pattern held across different contexts and analytical approaches. When the research team ran alternative statistical models and tested different ways of measuring heat exposure, the core finding persisted: sustained exposure to temperatures above 32°C during early childhood corresponded with lower developmental scores.

The biological mechanisms make sense. Young children’s brains are building trillions of neural connections during their first years, a process that requires enormous energy and depends on stable conditions. Heat stress diverts resources toward survival and cooling, potentially shortchanging the sophisticated brain development that distinguishes humans. The early years represent a sensitive period when environmental conditions can shape cognitive trajectories that persist throughout life.

If these early developmental patterns persist into later childhood and adulthood, the consequences could be far-reaching. Today’s three- and four-year-olds will reach their peak working years in the 2040s, when climate models project temperatures will continue rising. Whether heat exposure during early childhood translates into lasting cognitive differences remains an open question that will require years of follow-up research to answer definitively.

The study arrives as many regions confront unprecedented temperature extremes. Over one-third of children worldwide now experience frequent heatwaves, according to UNICEF estimates. Almost every child on earth already faces some downstream consequence of climate change, whether through disrupted agriculture, forced migration, or extreme weather.

For policymakers, the findings suggest that addressing climate change and supporting early childhood development can’t be separated. Investments in cooling infrastructure, clean water access, and basic services for poor families may serve double duty—both improving children’s immediate wellbeing and protecting their cognitive development.

The researchers emphasized that their measurements captured chronic exposure rather than acute events. Children living through day after day of temperatures exceeding 32°C may experience compounding effects that a single extreme heat wave wouldn’t produce. This distinction matters because climate change brings both—higher baseline temperatures and more frequent extreme events.

As the planet continues warming, the cognitive toll on each new generation of children may represent one of climate change’s most lasting and least visible costs. Unlike flooded coastlines or damaged infrastructure, the developmental effects occur silently, in the formation of neural pathways and the acquisition of skills that underpin everything children will later accomplish.

The study’s scope—examining development at ages three and four—raises questions about whether these effects persist, intensify, or fade as children age. Longitudinal research tracking the same children across years could reveal whether early heat exposure creates lasting disadvantages or whether later interventions can help children catch up.

For now, the evidence points to a troubling reality. Heat isn’t just making childhood uncomfortable. It may be making the next generation less prepared to solve the problems they’ll inherit, including the climate crisis itself.

---