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Millions of people already endure dangerous heat waves each year, and climate researchers warn that some of the world’s hottest and most humid regions could face even greater risks within the next 30 to 50 years. Research using NASA observations and climate models projects that parts of South Asia, the Persian Gulf, eastern China and other regions could periodically experience heat and humidity approaching the limits of human tolerance.
Scientists emphasize that these projections describe increasingly frequent episodes of extreme heat stress, rather than entire regions becoming permanently uninhabitable. Even so, they warn that unchecked global warming could severely disrupt public health, infrastructure, and daily life.
Why wet-bulb temperature is so dangerous
Air temperature tells only part of the story. Researchers focus on wet-bulb temperature because it combines heat and humidity into a single measure of how difficult it is for the body to release excess heat. When humidity rises, sweat evaporates more slowly, reducing the body’s main cooling mechanism. For healthy adults exposed outdoors without artificial cooling, scientists have long regarded a wet-bulb temperature of 35°C (95°F) as the upper theoretical limit for survival over several hours. More recent physiological research suggests that dangerous heat stress can develop at lower values, particularly among older adults, children, outdoor workers and people with chronic illnesses.
NASA explains that continued global warming will increase the frequency and intensity of these conditions. Instead of occurring only during exceptionally rare weather events, dangerous combinations of heat and humidity could become more common in regions that already experience prolonged summer heat. Researchers caution that the precise impacts will vary depending on local climate, public health measures, access to cooling, and future greenhouse gas emissions.
Regions where climate models project the greatest heat stress
Several regions appear consistently across climate projections because they combine high temperatures with persistent humidity. The Persian Gulf and the Red Sea rank among the most vulnerable areas, where warm coastal waters increase atmospheric moisture while air temperatures continue to rise. Northern India, Pakistan and Bangladesh also face elevated risk because millions of people already live in densely populated areas exposed to intense seasonal heat waves.
Climate models highlight eastern China and parts of Southeast Asia as future hotspots, driven in part by urban expansion that traps heat and prevents nighttime cooling. NASA-funded research indicates parts of Brazil could face similar conditions later this century. Meanwhile, sections of the central United States are projected to approach dangerous wet-bulb thresholds during severe heatwaves. Researchers highlight these regions not because they share the same climate, but because they combine environmental conditions that place greater stress on the human body during prolonged heat waves.
Scientists also point out that exposure does not affect everyone equally. Communities with reliable electricity, cooling systems, healthcare, drinking water and effective heat-warning programs generally cope better than places where those resources remain limited. For that reason, adaptation measures play a central role alongside efforts to reduce greenhouse gas emissions.
Colombia is warming, but scientists draw an important distinction
Colombia does not appear among the regions that climate studies identify as facing the highest projected wet-bulb temperatures during the coming decades. Even so, the country has experienced increasingly intense heat. According to Colombia’s Institute of Hydrology, Meteorology and Environmental Studies (IDEAM), several municipalities have recorded temperatures above 40°C (104°F) in recent years. Recent heatwaves have pushed temperatures to near-record highs across key departments, including Cesar, Magdalena, Tolima, and Cundinamarca.
Those observations reflect a broader warming trend rather than the same level of projected heat stress identified for South Asia or the Persian Gulf. High humidity in parts of Colombia’s Caribbean coast, the Magdalena Valley and other lowland regions can still increase the health risks associated with extreme temperatures, especially for people who work outdoors or lack access to cooling. IDEAM has also warned that longer and more frequent heat waves can increase pressure on water supplies, agriculture and public health.
Researchers caution that climate projections describe possible futures rather than fixed outcomes. How often dangerous heat conditions occur over the coming decades will depend largely on future greenhouse gas emissions and on how quickly governments strengthen adaptation measures. Expanding urban green spaces, improving heat-warning systems, protecting water resources and investing in resilient infrastructure can reduce the impact of extreme heat even in regions expected to warm the fastest.