Too Hot to Ignore: The Escalating Health Impact of Heatwaves in Brazil.

Heatwaves (HWs) are becoming more frequent and severe, posing a significant threat to human health. Studies have shown that extreme heat, whether as incremental temperature increases or prolonged HWs, is associated with an increased risk of heat-related illnesses. However, there is still limited understanding of how these impacts unfold in Brazil, given its unique social, environmental, and health-system contexts. I this perspective article, we explore the effects of HWs on human physiology, examine the social and biological factors that contribute to heat stress, and identify vulnerable populations at disproportionate risk. We also discuss the potential consequences of extreme heat in other aspects of society, such as agriculture and energy, and assess the challenges of strengthening resilience in Brazil's health sector. Our key contribution are to make visible the hidden burden of heat-related mortality, to examine how fragmented governance constrains the adaptive capacity of Brazil's health sector, and to reflect on pathways to strengthen resilience to heatwaves.