The health effects of extreme heat

Abstract

Extreme heat is a significant direct health threat from climate change, with rising temperatures and frequent heatwaves increasingly stressing communities and health services across Africa. High baseline temperatures, widespread outdoor labour, limited cooling access and structural vulnerabilities heighten population exposure. The physiological impacts are severe: from extreme heat overwhelming thermoregulation, leading to dehydration, cardiovascular strain, direct cellular injury and potentially rapid progression to heat exhaustion, to the most severe and dangerous form, heat stroke, which is a medical emergency characterised by a core body temperature > 40 °C and central nervous system dysfunction such as confusion, seizures or coma, leading to multiorgan dysfunction. Heat also exacerbates chronic conditions like heart failure, asthma and kidney disease. Beyond clinical presentations, community-level evidence shows heat causes sleep disturbance, irritability and significant reductions in productivity. Vulnerable groups include infants, older adults, pregnant women, individuals with chronic diseases and outdoor workers. Maternal and neonatal health is particularly at risk, with links to preterm birth, stillbirth and hypertensive disorders. Primary health care is central to addressing this threat through early recognition, prompt cooling, hydration, medication review and tailored counselling for low-resource settings and environments. A proactive integration of heat-health interventions into routine primary care is therefore critical to building climate-resilient health systems and safeguarding vulnerable populations.