At what temperature does heat become dangerous for humans?

People in Pakistan and many other countries around the world are currently experiencing extreme heat and heatwaves affecting millions in their daily lives.

In reality, due to climate change, both the intensity and duration of heatwaves have significantly increased. This is why many people often ask what level of temperature is considered too extreme for normal human activity. The answer is not simple as humidity in the air plays an equally important role alongside temperature.

A 2010 study suggested that in highly humid environments, 35°C is close to the upper limit of human survivability. Beyond this level, the human body is unable to cool itself effectively through sweating as sweat cannot evaporate properly leading to a rise in body temperature and increasing the risk of heatstroke.

In recent years, global temperatures have continued to rise and scientists are conducting further research on human heat tolerance. A 2023 study from the University of Roehampton in the UK found that at around 40°C, the human body begins to struggle significantly with temperature regulation and must work much harder to stay cool.

The study involved 13 adults who were exposed to different temperature and humidity conditions while resting for one hour. Experiments were conducted in environments ranging from 27°C to 50°C. Researchers observed that when temperatures reach 40°C, metabolic rate increases especially in conditions of high humidity.

According to researchers, the findings suggest that at temperatures between 40°C and 50°C, the human body faces extreme difficulty in maintaining thermal balance. The study also highlighted that not only high temperature but also high humidity poses a serious threat to human health.

A study from Pennsylvania State University in the United States in July 2023 found that when humidity exceeds 50%, the combination of heat and moisture can cause the human body to begin losing its ability to cool itself at around 31°C instead of 35°C.

Dry vs Humid conditions

The study explained that in dry and hot conditions, the body can effectively cool itself by evaporating sweat although there is a limit to how much sweat the body can produce. In such environments, humans may still manage daily activities even at around 40°C with caution.

However, in humid conditions even at lower temperatures—the strain on the heart and other bodily systems increases significantly. In such weather, temperatures above 30°C can already make it difficult for the body to regulate its internal heat.

Researchers also plan to conduct further studies on elderly individuals as aging reduces the body’s ability to tolerate extreme heat.