Extreme Heat Causes Developmental Delays in Young Kids: New Study

Young children exposed to extreme heat face significant hurdles in reaching essential developmental milestones, particularly in literacy and numeracy skills. A comprehensive study published on December 7, 2025, in the prestigious Journal of Child Psychology and Psychiatry examined data from nearly 20,000 preschool-aged children across six developing countries, uncovering a direct link between high temperatures and slowed early learning progress. Researchers found that children aged three and four experiencing average maximum temperatures exceeding 86°F (30°C) were 5% to 6.7% less likely to achieve these milestones compared to peers in cooler conditions below 78.8°F (26°C), even when accounting for factors like the same region, season, and household characteristics.

This effect persisted across diverse settings, highlighting how rising global temperatures due to climate change could undermine foundational cognitive growth that sets the stage for lifelong educational success.​ The study’s rigorous methodology combined UNICEF’s Multiple Indicator Cluster Surveys (MICS)—a globally trusted tool for assessing child well-being—with precise climate data from the ERA5-Land dataset covering monthly averages from 2017 to 2020.

By focusing on the Early Childhood Development Index (ECDI), which evaluates skills in literacy/numeracy (such as recognizing letters, counting to 10, or identifying shapes), physical development, socio-emotional abilities, and learning approaches, the analysis revealed the sharpest declines in literacy and numeracy—core building blocks for school readiness. These findings add to a growing body of evidence on heat’s broad impacts, from physical health risks like dehydration to cognitive disruptions, and underscore the urgency for global awareness as heatwaves become more frequent and intense worldwide.​

Vulnerable Populations Bear Greatest Burden

Certain groups shoulder the heaviest toll from heat exposure, amplifying existing inequalities in child development. The research drew from 19,607 children in Gambia, Georgia, Madagascar, Malawi, Palestine, and Sierra Leone—nations representing varied climates, economies, and urban-rural divides—showing that effects were most severe among children from economically disadvantaged households, those in urban environments with higher heat island effects, and families lacking access to clean water or proper sanitation. For instance, children in the poorest quintiles exhibited even wider gaps in milestone achievement during hot periods, as reported by Yale Environment 360, where limited resources prevent simple protections like fans, hydration, or shaded play areas.​

Lead author Jorge Cuartas, an assistant professor of applied psychology at NYU Steinhardt, emphasized in interviews that while heat’s harms on physical and mental health are known, this study illuminates its role in stunting early brain development across borders. Excessive heat negatively impacts young children’s development in diverse countries,” Cuartas stated, noting that early childhood forms the bedrock for lifelong learning, health, and well-being—making these results a wake-up call for researchers, governments, and communities. In regions like sub-Saharan Africa and the Middle East, where poverty intersects with climate vulnerability, such disparities could perpetuate cycles of educational underachievement for generations.​

Mechanisms and Policy Implications

Children’s unique physiology explains their heightened sensitivity to heat: their immature sweating mechanisms impair temperature regulation, leading to rapid dehydration, fragmented sleep, systemic inflammation, and elevated stress hormones like cortisol that hinder neural connections in the developing brain. Prolonged exposure disrupts daily routines—reducing playtime, outdoor exploration, and parent-child interactions critical for learning—while indoor heat in poorly ventilated homes compounds the issue, especially without air conditioning. The study controlled for confounders like maternal education, household wealth, and seasonal variations, confirming heat as an independent risk factor.​

Co-authors Lenin H. Balza and Nicolás Gómez-Parra from the Inter-American Development Bank, alongside Andrés Camacho from the University of Chicago, advocate for tailored climate adaptation measures, such as heat-resilient school designs, community cooling centers, and subsidies for fans or water access in at-risk areas. Cuartas called for expanded research into protective buffers—like nurturing caregiving or green urban planning—that could mitigate risks, urging policymakers to integrate child development into national climate strategies. As global temperatures climb, these insights demand proactive interventions to safeguard the most vulnerable, ensuring no child pays the price for a warming planet.