The intensifying heat stress poses significant risks to human health, particularly in regions already accustomed to high temperatures. Humid heat waves are especially dangerous as they hinder the body's ability to cool through sweating, increasing the risk of heat-related illnesses and fatalities. Vulnerable populations, including the elderly and those in low-income areas, are disproportionately affected. The study also notes that tropical nights, where temperatures remain above 68°F (20°C), prevent adequate recovery from daytime heat, further exacerbating health risks. Globally, one billion more people now face at least one day of extreme heat stress annually compared to the 1970s.