Heatwave

The severe heatwaves in India in 2025 have underscored the urgent need for more effective responses to heat stress and its impacts on human health, productivity, and the broader environment. As global temperatures rise, the frequency and intensity of these heatwaves are expected to increase, highlighting the critical need for short-term and long-term strategies to mitigate the consequences.

Heatwave in India

A heatwave is a prolonged period of abnormally high temperatures during the summer months, typically occurring between March and June. In rare cases, heatwaves can extend into July. The Indian Meteorological Department (IMD) defines and categorizes heatwaves using specific criteria based on maximum temperature, departure from normal temperature, and actual maximum temperature.

IMD Criteria for Defining Heatwaves:

1. Based on Maximum Temperature:

• Plains: A heatwave is declared when the maximum temperature is 40°C or more.

• Hilly Regions: A heatwave occurs when the temperature reaches 30°C or more.

• Coastal Areas: A heatwave is declared when temperatures exceed 37°C.

2. Based on Departure from Normal Maximum Temperature:

• When the normal maximum temperature is ≤ 40°C:

  • Heat Wave: If the departure from the normal temperature is 5°C to 6°C.

  • Severe Heat Wave: If the departure from normal temperature exceeds 7°C.

• When the normal maximum temperature is > 40°C:

  • Heat Wave: If the departure from the normal temperature is 4°C to 5°C.

  • Severe Heat Wave: If the departure from normal temperature exceeds 6°C.

3. Based on Actual Maximum Temperature:

• Heat Wave: Declared when the actual maximum temperature exceeds 45°C.

• Severe Heat Wave: Declared when the actual maximum temperature exceeds 47°C.

4. Declaration Criteria:

• The above conditions must be met in at least two stations within a Meteorological Sub-division.

• The conditions should persist for at least two consecutive days to qualify as a heatwave.

Key Causes of Heatwaves

1. Urban Heat Island Effect:

   • Urban areas, particularly metropolitan cities, experience higher temperatures than rural areas due to concrete buildings, lack of vegetation, and human activities. This creates localized microclimates, exacerbating the effects of heatwaves in densely populated regions.

2. Climate Change as a Driver:

   • Climate change plays a significant role in intensifying and extending the duration of heatwaves, as rising global temperatures alter weather patterns. For instance, the El Niño phenomenon can further raise temperatures, particularly during the summer months.

Socio-Economic Impacts of Heatwaves

1. Impact on Livelihoods:

   • With over 75% of India’s workforce engaged in heat-exposed labor (e.g., farming, construction), heat stress significantly hampers productivity. For example, 2023 studies revealed India lost 6% of work hours due to heat stress, resulting in 3%–5% GDP loss.

2. Agriculture and Food Security:

   • Rising temperatures harm crop yields and livestock survival, impacting farmers' income and food supply chains. Frequent power outages due to increased electricity demand further disrupt agriculture, especially irrigation and food processing.

3. Vulnerable Populations:

   • Women, elderly, migrants, and urban poor are disproportionately affected. For example:

     • Women working in poorly ventilated kitchens suffer additional heat stress.

     • Slum dwellers often live in areas with poor ventilation, limited green spaces, and high heat retention.

Challenges in Addressing Heatwaves

1. Inadequate Implementation of Heat Action Plans (HAPs):

   • HAPs often lack clear accountability, sufficient funding, and inter-agency coordination. Many plans are insufficiently implemented due to lack of local adaptation and integration with disaster management systems.

2. Poor Data Ecosystem:

   • There is underreporting of heat-related illnesses and deaths, which hinders the development of targeted interventions. Accurate data collection on morbidity and mortality is crucial for effective action.

3. Urban Vulnerabilities:

   • Slum areas, where many vulnerable populations reside, face amplified heat due to poor infrastructure, lack of green spaces, and dense concrete structures that trap heat.

4. Lack of Context-Specific Solutions:

   • A uniform ‘stay indoors’ advisory is often impractical for the poor, especially those living in heat-retaining homes. Tailored solutions are necessary to address the varied needs of different populations.

5. Insufficient Public Infrastructure:

   • There is limited access to basic relief measures like drinking water, shaded shelters, and Oral Rehydration Salts (ORS), especially in heat-prone areas.

India’s Heat Action Plans (HAPs)

India’s response to heatwaves began in 2013 with Ahmedabad’s Heat Action Plan (HAP), the first of its kind in Asia. As of now, 23 States and over 140 cities have formulated HAPs. These plans generally include:

• Early warnings and public alerts,

• Community awareness campaigns,

• Health system preparedness,

• Long-term mitigation measures like urban greening and cool roofing,

• Data collection on morbidity and mortality related to heat.

National Programme on Climate Change and Human Health (NPCCHH):

This program, coordinated by the National Disaster Management Authority (NDMA), focuses on heat advisories, health alerts, and the overall preparedness for climate-related health issues.

Way Forward

Short-Term Measures

1. Strengthen Heat Action Plans:

   • Make HAPs dynamic and locally tailored to specific cities, ensuring they are well-integrated with disaster management frameworks and are regularly updated.

2. Early Warning Systems:

   • Expand the use of Indian Meteorological Department (IMD) forecasts and mobile alerts to notify vulnerable populations in real-time, ensuring timely actions can be taken.

3. Immediate Relief Measures:

   • Ensure the availability of drinking water, shaded shelters, ORS distribution, and heat-safe work guidelines in affected areas.

4. Targeted Heat Advisories:

   • Issue region-specific warnings that account for factors like humidity, vulnerability, and occupation-based risks (e.g., outdoor workers).

Long-Term Strategies

1. Climate-Resilient Urban Planning:

   • Promote cool roofing, reflective paints, green cover, and sustainable architecture to reduce the urban heat island effect. Tree planting in cities can also help mitigate heat effects.

2. Summer Shelters and Cooling Centers:

   • Establish safe zones like ‘summer shelters’ and cooling centers to provide hydration and rest for the homeless, migrant workers, and those working in high-heat environments.

3. Skill Development and Employment Reform:

   • Introduce heat-resilient construction techniques and staggered work hours to reduce exposure for outdoor laborers, especially in construction and agriculture.

4. Insurance and Social Protection:

   • Offer wage insurance for workers affected by extreme heat and provide subsidized health support for heat-affected individuals.

5. Integrated Climate Governance:

   • Mainstream climate adaptation across various sectors such as urban planning, agriculture, health, and labor to ensure a holistic and coordinated approach to managing heatwaves.

6. Consider Heatwaves as a Notified Disaster:

   • There is an ongoing debate about including heatwaves under the Disaster Management Act, 2005 to ensure better coordination and resource allocation. However, challenges like financial implications and the difficulty in attributing deaths directly to heatwaves remain.

Conclusion

India's response to the heatwave crisis must be multifaceted, integrating short-term relief measures with long-term climate resilience strategies. As climate change accelerates, the country will need to adapt its urban planning, workforce management, and health infrastructure to address the growing heat stress problem.