India Headed for More Humid, Prolonged Heat Stress, Warns IIT Roorkee, Lisbon University Study

Dehradun: A recent study conducted by researchers from the Indian Institute of Technology (IIT) Roorkee and the University of Lisbon has raised alarms about the future climate of India. The study, published in the peer-reviewed journal Scientific Reports, highlights that excessive heat and humidity observed during the summer of 2025 may serve as an early indicator of the severe heat stress conditions expected to become more common across the country.

Key Findings of the Study

The researchers warn that heat stress in India is projected to become longer, more intense, and increasingly regional in nature. This is primarily due to rising temperatures combined with increasing humidity, which will significantly amplify health risks associated with heat exposure.

Heat Index as a Measure of Heat Stress

Unlike traditional assessments that focus solely on air temperature, this study utilizes the Heat Index, which indicates how hot conditions feel to the human body when high humidity limits the evaporation of sweat. The findings suggest that India has already experienced significant warming since the 1980s, with winter temperatures rising faster than summer temperatures. This trend is linked to declining Himalayan snow cover and fewer cold-air intrusions.

Projected Increase in Dangerous Heat Conditions

According to the study, by the mid-21st century (2041–2070), the annual number of days experiencing dangerous heat conditions is expected to rise sharply across large parts of the country. Key projections include:

• Days with a Heat Index exceeding 27°C, associated with fatigue and heat stress, could increase by over 50 days per year compared to the late 20th century.
• Days with a Heat Index exceeding 32°C, considered extremely dangerous and linked to heat exhaustion and heat stroke, are also projected to become more frequent.
• Under a high-emissions scenario, India could face more than 75 days each year with Heat Index values above 27°C during the summer monsoon season alone by the end of the century.

Regional Variations in Heat Stress

The study highlights stark regional contrasts in how heat stress is likely to unfold across India:

• Coastal regions are expected to experience higher heat stress even during winter months due to rising humidity.
• Northern and inland areas are likely to face the most severe conditions during summer.
• Even the Himalayan region, traditionally buffered by cooler temperatures, will not be immune to these changes. Continued warming and shrinking snow cover are expected to increase exposure over time.

Prolonged Heat Events

One of the most concerning findings of the study is the persistence of heat events. The researchers found that not only will heat-stress days become more frequent, but heat spells will also last longer. Under unchecked emissions, prolonged episodes of extreme heat lasting from 20 to 75 consecutive days could become widespread. Public health experts have warned that such sustained exposure significantly increases the risk of illness and death, particularly among vulnerable groups such as outdoor workers, the elderly, and the urban poor.

Implications for Public Health and Urban Planning

The findings of this study carry major implications for various sectors, including:

• Public Health: Increased heat stress will likely lead to higher rates of heat-related illnesses and fatalities.
• Labour Safety: Outdoor workers will face heightened risks, necessitating new safety protocols and regulations.
• Urban Planning: Cities will need to adapt infrastructure to cope with rising temperatures and humidity, including better cooling systems and green spaces.
• Water and Energy Management: Increased demand for cooling will stress water and energy resources, requiring innovative management strategies.

Call for Action

The study emphasizes the need for region-specific heat action plans that take into account both temperature and humidity. Researchers advocate for immediate action to mitigate the impacts of climate change and prepare for the expected rise in heat stress conditions.

Conclusion

As India faces an uncertain climate future, the findings from IIT Roorkee and the University of Lisbon serve as a crucial reminder of the urgent need for comprehensive strategies to address the impending challenges posed by prolonged heat stress. The time to act is now to safeguard public health and ensure sustainable development in the face of climate change.

Note: The information presented in this article is based on a study published in Scientific Reports and reflects the current understanding of climate trends in India as of 2023.