New Delhi: A new satellite-based analysis by an environmental think-tank, tracking 247 municipal wards of Delhi during the summer from 2015 to 2026, found that the city had been recording a rise in the heat level.According to Envirocatalyst, which processes Landsat imagery at 30-metre resolution, Delhi’s mean land surface temperature (LST) rose from 29.1 degrees Celsius in March 2015 to 32 in March 2026, a rise of 2.8 degrees in 11 years. Annual swings ranged from as low as -4.5 degrees in a single year to as high as +3.1 degrees, but the 11-year net was always rising, corresponding to the shift in the air temperature recorded at Safdarjung.Data shows that the highest average LST in May from 2015 to 2025 was recorded at Isapur in Najafgarh zone at 50.7 degrees Celsius, while the city’s average for the month was 44.1. Experts said the air temperature was usually lower than the surface temperature due to meteorological conditions, including wind patterns and humidity levels.The heat intensity varies ward-wise. Sangam Vihar A, a dense residential colony in south Delhi, recorded the steepest March LST increase of 6.1 degrees between 2015 and 2026, and Meethapur, Sangam Vihar-B, Madangir and Tigri rose between 4.9 and 5.2 degrees over the same period. However, Prem Nagar and Isapur saw the lowest rise of just 0.6 degrees during the same period.In March 2026, the hottest wards were Mahipalpur at 34.4°C and Harkesh Nagar at 34°C. The coolest, Nangal Thakran, recorded 29.2°C. “Five degrees of difference within the same city, in the same month, under the same official weather alert,” stated the analysis.“The important point of this analysis is that it shows which locations in Delhi need localised heat adaptation plans and granular policy changes,” said Sunil Dahiya, founder of Envirocatalyst. “Areas that once had parks, waterbodies or small vegetation cover were replaced by constructed surfaces. That directly contributes to the rise in surface temperature.”In April, Delhi’s mean LST rose by 3.5 degrees between 2015 and 2025. Bhati recorded the highest April increase at 6.1 degrees, followed by Madanpur Khadar East and Badarpur at 5.9 degrees each.In May and June, each of the wards was in the strong heat stress zone with a universal thermal climate index (UTCI) above 32 degrees Celsius every year from 2015 to 2025. In May, surface temperatures touched 52 degrees Celsius in some wards, including Anand Vihar, Badarpur, Chhawla, Dilshad Colony, Dilshad Garden, Gharoli, Hari Nagar Extension, Harkesh Nagar, IP Extension, Isapur, Jhilmil, Kalyanpuri, Pul Prahladpur, Meethapur, Sarita Vihar and Tughlaqabad. In June, a delayed monsoon pushed the city mean close to or above 47 degrees Celsius in years like 2019 (47.6 degrees Celsius) and 2024 (46.9 degrees Celsius).The UTCI data for March tells the most striking story of 2026. “In 2015, no ward in Delhi crossed the 26 degree Celsius moderate heat stress threshold. That figure barely moved through the next decade. In March 2025, just one ward crossed it. In March 2026, all 247 wards crossed it simultaneously. It is the first time in the 11-year satellite record that March has left no ward of Delhi at thermal rest,” revealed the analysis.Experts said there was a need to prepare localised heat action or adaptation focussing on ward cooling shelters, natural construction materials and greening of urban corridors. “While we discuss other urban challenges, we cannot afford to miss the compounding threat of heat stress. This ward-level data can be used by govt and policymakers to make real-time, localised decisions,” said Dahiya.