Researchers at NASA’s Jet Propulsion Laboratory have identified a troubling pattern: the heat threshold at which the human body begins to fail is becoming far more common than it was in 1979. The findings, published in Science Advances, bring renewed urgency to discussions about how rising global temperatures will shape daily life and health in both North America and beyond.
Experts explain that a healthy young person can barely survive a single day in conditions where the air temperature sits at 35 °C (95 °F) with 100 percent humidity. Even when water is plentiful and shade is available, the body’s main cooling mechanism — evaporation of sweat — stalls in such extreme humidity. Without effective sweating, core temperature climbs, and the risk of heat-related illness increases rapidly, potentially leading to serious injury or death in a matter of hours.
According to the study, instances of these ultra-extreme conditions have been recorded about a dozen times in recent decades, with most episodes occurring in regions such as South Asia and the Persian Gulf. Notably, none of those heat events persisted longer than two hours, yet they underscored a fragile boundary between environmental stress and human safety. The pattern implies that brief bursts of extreme heat can occur even under seemingly manageable circumstances, creating an ongoing challenge for health systems and urban planning alike.
What makes the last four decades so alarming is the pace and frequency of these intense heat spikes. The researchers find that occurrences have more than doubled since 1979, signaling a shift in how often hot conditions reach levels that overwhelm the body’s cooling system. Projections indicate that, if global temperatures rise about 2.5°C above pre-industrial levels, many regions could experience regular days with temperatures above 35°C. In such scenarios, five to seven hours in these conditions could be enough to begin harming health, particularly for vulnerable groups such as outdoor workers, the chronically ill, or children. The message is clear: heat stress is becoming a more common, everyday risk rather than a rare event—one that demands proactive adaptation in housing, infrastructure, and public health response across Canada, the United States, and neighboring regions.
The study also highlights a practical concern that often surfaces in hot weather: the risk of dehydration and kidney stones. When the body loses fluids rapidly through sweating, the kidneys must work harder to balance minerals and hydrate the system. In environments where water intake is constrained by heat or access challenges, the risk of kidney stone formation can rise. The intersection of high heat and limited hydration creates a cycle that raises the probability of stone development, especially for individuals who spend long periods outdoors or in high-heat occupations. Public health guidance during extreme heat events emphasizes staying hydrated, seeking cooler environments, and monitoring for symptoms such as intense thirst, dark urine, or pain that could indicate kidney stones. For communities and workplaces in hot regions, practical measures include cooling centers, shaded rest areas, and readily available water and electrolyte solutions to support kidney and overall health as temperatures climb.
When planning for a hotter future, researchers urge a combination of personal precautions and systemic changes. On an individual level, people should pace their activities to avoid peak heat, wear breathable clothing, and stay informed about local heat advisories. At the community level, urban designers and policymakers can reduce heat through reflective building materials, urban greening, and efficient cooling systems in public buildings. Employers may consider adjusted work schedules, mandatory breaks, and accessible hydration stations to protect outdoor workers and others exposed to high temperatures. Taken together, these strategies can help reduce the health impact of rising heat while maintaining productivity and quality of life across North America.
Ancient scientists once explored ways to prevent health issues linked to heat and mineral balance in the body. Modern researchers now translate those ideas into actionable advice for today’s hot climates, focusing on hydration strategies, electrolyte balance, and early detection of heat-related symptoms. Through ongoing observation and cross-disciplinary collaboration, the scientific community continues to improve guidance for reducing heat risk and supporting kidney health in warmer environments. These efforts underscore a practical, evidence-based approach to staying safer as temperatures trend higher in the coming years, and they serve as a reminder that proactive preparation matters just as much as immediate response in safeguarding health during extreme heat events.