Extreme heat in India is increasing both in frequency and intensity. Delhi recorded its warmest night in six years while India experienced over 280 heatwave days between March and May 2022. Additionally In June 2024 alone, the country logged more than 40,000 suspected heat-stroke cases and at least 110 confirmed deaths, figures experts believe are substantial undercounts. 

The consequences of rising temperatures extend beyond health, contributing to economic losses—heat stress could reduce India’s GDP by an estimated 4.5% and threaten 35 million jobs by 2030. Urban areas are particularly affected due to the Urban Heat Island effect, where built environments can be up to 6 °C hotter than surrounding rural areas, and variations within cities are stark. 

Understanding the spatial distribution of heat exposure and its differential impacts on health and productivity is critical for designing targeted, equitable heat action plans. This report responds to this need by examining how urban form, housing conditions and socio-economic vulnerability shape heat risk in Delhi.

Read the report here

Our methodology triangulates satellite based micro-climate data, neighbourhood level built environment characteristics, and household survey data to identify the drivers of heat vulnerability in Delhi. This integrated approach captures both spatial variation in heat exposure and differences in households’ ability to cope with extreme temperatures.

The analysis was conducted in three steps:

• Geospatial heat mapping: High resolution satellite data on built-up area, tree cover, and experienced heat (ERA5-Land and VIIRS) were integrated to build neighbourhood level micro-climate profiles across Delhi
• Citizen data integration: Households to survey were identified (2,368 households across all 70 Assembly Constituencies) and were spatially linked to capture neighbourhood level variation in experienced heat
• Survey implementation: Primary in-person surveys conducted during peak summer captured socio-economic characteristics, energy use and heat-related health and productivity impacts.

    1. Spatial Heat Baseline – Factors shaping experienced heat

• • When built-up surface area increases from about 25% to 55%, experienced temperatures rise by roughly 0.6°C demonstrating how the Urban Heat Island effect can vary dramatically across short distances due to small differences in built area.
  • We found that a rise in green cover from about 3% to 11% is associated with roughly a 1°C drop in experienced heat, showing that even modest increases in green cover can substantially reduce local heat stress.

     2. Coping Capacity/ Adaptation: Household Appliances, Occupation and Commute

• • Our findings show that rising heat sharply worsens sleep: with the worst sleep concentrated in the 42.5–47°C range.
  • Access to cooling dramatically reduces this burden, however this is unequal as AC-owning households spend nearly twice as much on electricity, while lower-asset households lack both appliances and the financial flexibility to increase cooling as temperatures rise.

3. Outcomes: Impact on Health and Productivity 

1. • A 3°C increase in temperature corresponded with a 15 percentage point rise in reported illness. Further, AC ownership is associated with about an 11.6% lower incidence of heat-induced illness
   • A 3°C increase in experienced heat shows a 10 percentage point jump in households missing work, from about 18% to nearly 28%. Further, AC owners report 18% lesser incidence of work loss compared to non-ac owners
   • Respondents reporting heat-related changes in mental state jump from 15% to 30% as heat increases by 3°C.