Abstract
This study investigates the climate change signal on mean and extreme temperatures in India, adding new insight by using the state-of-the-art CMIP6 projections to quantify the seasonal and spatial evolution of the Heat Index (HI) across India.; offering one of the first national-scale assessments combining temperature and humidity under Shared Socioeconomic Pathways (SSPs) scenarios. To assess the recent past climate change signal on those properties, ERA5 reanalysis data are used. CMIP6 models realistically reproduce historical warming patterns during winter (DJF) and pre-monsoon (MAM) seasons but tend to underestimate extreme summer (JJA) conditions. Future daily HI is calculated from maximum temperature and relative humidity from CMIP6 global climate models (GCMs). Future projections indicate a substantial increase in both the frequency and persistence of dangerous HI levels across India, driven by rising temperatures and regionally variable humidity trends. By mid-21st century (2041–2070), the annual number of days with dangerously high HI values (27º and 32 °C) is projected to rise by more than 50 and 5 days, respectively, compared to 1971–2000. By the late century (2071–2100) under the SSP5-8.5 scenario, the HI will be above 27 °C (32 °C) during more than 75 (75) absolute days per year in JJA and more than 75 (20) days in MAM. Critical HI days will be highest in coastal regions in winter and more northern regions in summer, increasing towards northern latitudes with the emission scenario. These findings underscore the importance of region-specific adaptation strategies, as heat stress future anomalies will differ across India. Understanding these spatiotemporal patterns is critical for effective climate adaptation and public health policies aimed at mitigating the increasing risks associated with extreme heat events.
Data availability
The data cannot be made publicly available upon publication because no suitable repository exists for hosting data in this field of study. The data that support the findings of this study are available upon reasonable request from M.O. Molina (mosanchez@ciencias.ulisboa.pt).
References
Patterson, M. North-west Europe hottest days are warming twice as fast as mean summer days. Geophys. Res. Lett. 50, e2023GL102757 (2023).
Schmidt, G. World view. Nature 627, 467 (2024).
Molina, M. O. et al. Updated insights on climate change-driven temperature variability across historical and future periods. Clim. Change. 178 (5), 97 (2025).
Alvarez, I., Diaz-Poso, A., Lorenzo, M. N. & Roye, D. Heat index historical trends and projections due to climate change in the mediterranean basin based on CMIP6. Atmos. Res. 308, 107512 (2024).
Eekhout, J. P. C., Nunes, J. P., Tramblay, Y. & de Vente, J. Severe impacts on water resources projected for the mediterranean basin. Wiley Interdiscipl. Rev. Water 12 (2), e70012 (2025).
Dahl, T. A., Lusk, D., Vizuete, W., Buser, J. & Spero, T. An air quality and public health perspective for the future of the epa’s air quality index. J. Air Waste Manage. Assoc. 69 (1), 1–13 (2019).
Sabater, S. et al. Extreme weather events threaten biodiversity and functions of river ecosystems: evidence from a meta‐analysis. Biol. Rev. 98 (2), 450–461 (2023).
Nath, R., Nath, D. & Chen, W. Projected changes in extreme hot summer events in Asian monsoon regions. Npj Clim. Atmospheric Sci. 7 (1), 188 (2024).
Carleton, T. et al. Valuing the global mortality consequences of climate change accounting for adaptation costs and benefits. Q. J. Econ. 137, 2037–2105 (2022).
Coffel, E. D., Horton, R. M. & De Sherbinin, A. Temperature and humidity based projections of a rapid rise in global heat stress exposure during the 21st century. Environ. Res. Lett. 13 (1), 014001 (2017).
Horton, R. M., Mankin, J. S., Lesk, C., Coffel, E. & Raymond, C. A review of recent advances in research on extreme heat events. Curr. Clim. Change Rep. 2, 242–259 (2016).
Di Napoli, C., Pappenberger, F. & Cloke, H. L. Verification of heat stress thresholds for a health-based heat-wave definition. J. Appl. Meteorol. Climatol. 58 (6), 1177–1194 (2019).
Blazejczyk, K., Epstein, Y., Jendritzky, G., Staiger, H. & Tinz, B. Comparison of UTCI to selected thermal indices. Int. J. Biometeorol. 56, 515–535 (2012).
Raymond, C., Singh, D. & Horton, R. Spatiotemporal patterns and synoptics of extreme wet-bulb temperature in the contiguous united States. J. Geophys. Res. Atmos. 122, 13–108 (2017).
Heo, S., Bell, M. L. & Lee, J. T. Comparison of health risks by heat wave definition: applicability of wet-bulb Globe temperature for heat wave criteria. Environ. Res. 168, 158–170 (2019).
Kjellström, T., Maître, N., Saget, C., Otto, M. & Karimova, T. Working on a Warmer Planet: the Effect of Heat Stress on Productivity and Decent Work (International Labour Organization, 2019).
McGregor, G. R. & Vanos, J. K. Heat: a primer for public health researchers. Public. Health. 161, 138–146 (2018).
Sherwood, S. C. How important is humidity in heat stress? J. Geophys. Res. Atmos. 123, 11–808 (2018).
Zhu, J., Wang, S. & Huang, G. Assessing climate change impacts on human-perceived temperature extremes and underlying uncertainties. J. Geophys. Res. Atmos. 124, 3800–3821 (2019).
Fischer, E. M. & Schär, C. Consistent geographical patterns of changes in high-impact European heatwaves. Nat. Geosci. 3, 398–403 (2010).
Pal, J. S. & Eltahir, E. A. Future temperature in Southwest Asia projected to exceed a threshold for human adaptability. Nat. Clim. Change. 6, 197–200 (2016).
Russo, S., Sillmann, J. & Sterl, A. Humid heat waves at different warming levels. Sci. Rep. 7, 7477 (2017).
de Freitas, C. R. & Grigorieva, E. A. A comparison and appraisal of a comprehensive range of human thermal climate indices. Int. J. Biometeorol. 61, 487–512 (2017).
Anderson, G. B., Bell, M. L. & Peng, R. D. Methods to calculate the heat index as an exposure metric in environmental health research. Environ. Health Perspect. 121 (10), 1111–1119 (2013).
Broede, P. et al. The universal thermal climate index UTCI compared to ergonomics standards for assessing the thermal environment. Ind. Health. 51 (1), 16–24 (2013).
Steadman, R. G. The assessment of sultriness. Part I: a temperature-humidity index based on human physiology and clothing science. J. Appl. Meteorol. Climatol. 18, 861–873 (1979).
Perkins, S. E. & Alexander, L. V. On the measurement of heat waves. J. Clim. 26 (13), 4500–4517 (2013).
Jin, Q. & Wang, C. A revival of Indian summer monsoon rainfall since 2002. Nat. Clim. Change. 7, 587–594 (2017).
Joseph, L., Skliris, N., Dey, D., Marsh, R. & Hirschi, J. Increased summer monsoon rainfall over Northwest India caused by Hadley cell expansion and Indian ocean warming. Geophys. Res. Lett. 51, e2024GL108829 (2024).
Shukla, K. K. & Attada, R. CMIP6 models informed summer human thermal discomfort conditions in Indian regional hotspot. Sci. Rep. 13, 12549 (2023).
Kumar, P., Rai, A., Upadhyaya, A. & Chakraborty, A. Analysis of heat stress and heat wave in the four metropolitan cities of India in recent period. Sci. Total Environ. 818, 151788 (2022).
Kothawale, D., Revadekar, J. V. & Rupa Kumar, K. Recent trends in pre-monsoon daily temperature extremes over India. J. Earth Syst. Sci. 119, 51–65 (2010).
Ma, Y. et al. Effects of extreme temperatures on hospital emergency room visits for respiratory diseases in Beijing, China. Environ. Sci. Pollut. Res. 26, 3055–3064 (2019).
Rocque, R. J. et al. Health effects of climate change: an overview of systematic reviews. BMJ open. 11, e046333 (2021).
Norgate, M., Tiwari, P. R., Das, S. & Kumar, D. On the heat waves over India and their future projections under different SSP scenarios from CMIP6 models. Int. J. Climatol. 44 (3), 973–995 (2024).
Dubey, S. K., Singh, R., Singh, S. K. & Maurya, S. K. Heatwave projections over India under different SSP scenarios using CMIP6 models. Environ. Res. Lett. 18 (6), 064018 (2023).
Molina, M., Sánchez, E. & Gutiérrez, C. Future heat waves over the mediterranean from an Euro-CORDEX regional climate model ensemble. Sci. Rep. 10, 8801 (2020).
Mukherjee, S. & Mishra, V. A sixfold rise in concurrent day and night-time heatwaves in India under 2ºC warming. Sci. Rep. 8, 16922 (2018).
Ramarao, M. et al. Projected changes in heatwaves over central and South America using high-resolution regional climate simulations. Sci. Rep. 14, 23145 (2024).
Hersbach, H. et al. The ERA5 global reanalysis. Q. J. R. Meteorol. Soc. 146, 1999–2049 (2020).
Hersbach, H. et al. Global reanalysis: goodbye ERA-Interim, hello ERA5. ECMWF Newsl. 2019, 17–24 (2019).
Eyring, V. et al. Overview of the coupled model intercomparison project phase 6 (CMIP6) experimental design and organization. Geosci. Model Dev. 9, 1937–1958 (2016).
Taylor, K. E. Truly conserving with Conservative remapping methods. Geosci. Model Dev. 17 (1), 415–430. https://doi.org/10.5194/gmd-17-415-2024 (2024).
Srivastava, A. K., Rajeevan, M. & Kshirsagar, S. R. Development of a high resolution daily gridded temperature data set (1969–2005) for the Indian region. Atmospheric Sci. Lett. 10 (4), 249–254 (2009).
Rohit, N. & N., C. Development of high Spatial resolution weather data using daily meteorological observations over Indian region. MAUSAM (2021). https://doi.org/10.54302/mausam.v71i4.43.
Hansen, J., Sato, M. & Ruedy, R. Perception of climate change. Proc. Natl. Acad. Sci. U S A. 109 (47), E2415–E2423 (2012).
Jain, M., Kumar, D., Kumar, P. & Singh, N. Assessing the reliability of CMIP6 climate models in simulating heatwave characteristics over India. J. Earth Syst. Sci. 132 (1), 127 (2023).
Almazroui, M., Islam, M. N., Saeed, S., Saeed, F. & Ismail, M. Future changes in climate over the Arabian Peninsula based on CMIP6 multimodel simulations. Earth Syst. Environ. 4, 611–630 (2020).
Zha, J. et al. Projected changes in global terrestrial near-surface wind speed in 1.5°C–4.0°C global warming levels. Environ. Res. Lett. 2021, 16. https://doi.org/10.1088/1748-9326/ac2fdd (2021).
Tebaldi, C. et al. Climate model projections from the scenario model intercomparison project (ScenarioMIP) of CMIP6. Earth Syst. Dyn. https://doi.org/10.5194/ESD-12-253-2021 (2020).
IPCC. Climate change : impacts, adaptation, and vulnerability. In Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, 2022).
Rothfusz, L. P., & Headquarters, N. S. R. (1990). The heat index equation (or, more than you ever wanted to know about heat index). Fort Worth, Texas: National Oceanic and Atmospheric Administration, National Weather Service, Office of Meteorology, 9023, 640.
Rothfusz, L. P. The heat index equation (2019, accessed 2 Dec 2024). https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml.
Brimicombe, C. et al. Thermofeel: a python thermal comfort indices library. SoftwareX 18, 101005 (2022).
Vaidyanathan, A. et al. Assessment of extreme heat and hospitalizations to inform early warning systems. Proc. Natl. Acad. Sci. 116 (12), 5420–5427 (2019).
Hunter, J. D. Matplotlib: a 2D graphics environment. Comput. Sci. Eng. 9 (03), 90–95 (2007).
Screen, J. A. & Simmonds, I. The atmospheric response to Arctic sea-ice loss in the CMIP5 climate models. J. Clim. 27, 4775–4793 (2014).
Cohen, J. et al. Arctic sea-ice loss and the mid-latitude winter climate. Nat. Clim. Change. 8 (3), 253–261 (2018).
Krishnan, R. et al. Unprecedented warming in the Hindu Kush himalaya. Nat. Clim. Change. 9 (1), 86–92 (2019).
Dimri, A. P., Singh, M., Niyogi, D. & Krishnan, R. Weather and climate extremes over the Hindu Kush himalaya: present status and future projections. Earth Sci. Rev. 222, 103822 (2021).
J Parker, D. et al. The interaction of moist convection and mid-level dry air in the advance of the onset of the Indian monsoon. Q. J. R. Meteorol. Soc. 142 (699), 2256–2272 (2016).
Roxy, M. K., Ritika, C., Terray, P. & Murtugudde, R. Drying of Indian Subcontinent is already underway. Nat. Commun. 6, 7306 (2015).
Mishra, V., Thirumalai, K., Singh, D. & Aadhar, S. Future exacerbation of hot and dry summer monsoon extremes in India. Npj Clim. Atmospheric Sci. 3 (1), 10 (2020).
Overland, J. E., Zhang, X. & Walsh, J. E. Arctic amplification: its role in middle-latitude climate change. Earth Sci. Rev. 191, 150–165 (2019).
Dutta, U. et al. Unraveling the global teleconnections of Indian summer monsoon clouds: expedition from CMIP5 to CMIP6. Glob. Planet Change. 215, 103873 (2022).
Molina, M. O. et al. The added value of simulated near-surface wind speed over the Alps from a km-scale multimodel ensemble. Clim. Dyn. 62 (6), 4697–4715 (2024).
Raghuvanshi, S., Dimri, A. P. & Sinha, V. Changes in spatio-temporal characteristics of extreme rainfall events over India under different SSPs. J. Geophys. Res. Atmos. 129 (1), e2023JD039757 (2024).
Raymond, C., Matthews, T. & Horton, R. M. The emergence of heat and humidity too severe for human tolerance. Sci. Adv. 6 (19), eaaw1838 (2020).
Rohini, P., Rajeevan, M. & Srivastava, A. K. On the variability and increasing trends of heat waves over India. Sci. Rep. 6 (1), 1–9 (2016).
Mazdiyasni, O. et al. Increasing probability of mortality during Indian heat waves. Sci. Adv. 3 (6), e1700066 (2017).
Sardana, D. & Agarwal, A. Impact of spring sea ice variability in the Barents–Kara region on the Indian summer monsoon rainfall. Sci. Rep. 15, 37790 (2025).
Pepin, N. et al. Elevation-dependent warming in mountain regions of the world. Nat. Clim. Chang. 5, 424–430 (2015).
Praveen, B. et al. Analyzing trend and forecasting of rainfall changes in India using non-parametrical and machine learning approaches. Sci. Rep. 10 (1), 10342 (2020).
Choudhary, R. K. et al. Excess mortality risk due to heat stress in different climatic zones of India. Environ. Sci. Technol. 58 (1), 342–351 (2023).
Gusain, A., Ghosh, S. & Karmakar, S. Added value of CMIP6 over CMIP5 models in simulating Indian summer monsoon rainfall. Atmos. Res. 232, 104680 (2020).
Singh, R. N. et al. Innovative trend analysis of spatio-temporal variations of rainfall in India during 1901–2019. Theoret. Appl. Climatol. 145 (1–2), 821–838 (2021).
Saha, M. & Singh, C. Evaluation of the characteristics of Indian summer monsoon simulated by CMIP6 models. Int. J. Climatol. 44 (9), 2833–2851 (2024).
Basha, G. et al. Historical and projected surface temperature over India during the 20th and 21st century. Sci. Rep. 7 (1), 2987 (2017).
Guntu, R. K., Merz, B. & Agarwal, A. Increased likelihood of compound dry and hot extremes in India. Atmos. Res. 290, 106789 (2023).
Ren, Y. Y. et al. Observed changes in surface air temperature and precipitation in the Hindu Kush Himalayan region over the last 100-plus years. Adv. Clim. Change Res. 8 (3), 148–156 (2017).
Kushwaha, R., Kumar, P. & Hisaki, Y. Global future heat stress projections: regional variations of humidex changes from high-resolution CMIP6 models. Atmos. Res. 2025, 108367 (2025).
Li, D., Yuan, J. & Kopp, R. E. Escalating global exposure to compound heat-humidity extremes with warming. Environ. Res. Lett. 15 (6), 064003 (2020).
Fischer, E. M. & Knutti, R. Robust projections of combined humidity and temperature extremes. Nat. Clim. Change. 3, 126–113 (2013).
Kysely, J. & Kim, J. Mortality during heat waves in South Korea, 1991 to 2005: how exceptional was the 1994 heat wave? Climate Res. 38 (2), 105–116 (2009).
Zanobetti, A. & Schwartz, J. Air pollution and emergency admissions in Boston, MA. J. Epidemiol. Community Health. 60 (10), 890–895 (2006).
Di Napoli, C., Barnard, C., Prudhomme, C., Cloke, H. L. & Pappenberger, F. ERA5-HEAT: a global gridded historical dataset of human thermal comfort indices from climate reanalysis. Geosci. Data J. 8 (1), 2–10 (2021).
Dahl, K., Licker, R., Abatzoglou, J. T. & Declet-Barreto, J. Increased frequency of and population exposure to extreme heat index days in the united States during the 21st century. Environ. Res. Commun. 1 (7), 075002 (2019).
Hoang, T. L. T. et al. Assessing heat index changes in the context of climate change: a case study of Hanoi (Vietnam). Front. Earth Sci. 10, 897601. https://doi.org/10.3389/feart.2022.897601 (2022).
Maraun, D. et al. Towards process-informed bias correction of climate change simulations. Nat. Clim. Change 7 (11), 764–773 (2017).
Nahar, J., Johnson, F. & Sharma, A. Addressing Spatial dependence bias in climate model simulations—an independent component analysis approach. Water Resour. Res. 54 (2), 827–841 (2018).
Zhang, H., Chapman, S., Trancoso, R., Toombs, N. & Syktus, J. Assessing the impact of bias correction approaches on climate extremes and the climate change signal. Meteorol. Appl. 31 (3), e2204 (2024).
Velpuri, M., Das, J. & Umamahesh, N. Spatio-temporal compounding of connected extreme events: projection and hotspot identification. Environ. Res. 235, 116615 (2023).
Acknowledgements
This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2023 , LA/P/0068/2020 e UID/50019/2025 https://doi.org/10.54499/LA/P/0068/2020) and https://doi.org /10.54499/UID/PRR/50019/2025. M.O. Molina was supported by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) through the DRI/India/0098/2020 project (https://doi.org/10.54499/DRI/India/0098/2020), the Instituto Dom Luiz through the UID/PRR/50019/2025 (https://doi.org/10.54499/UID/PRR/50019/2025), and by the Horizon Europe research and innovation programs under grant agreement no. 101081661 (WorldTrans). AA extends thanks to the Anusandhan National Research Foundation for the research grant (CRG/2023/003449) facilitated at IIT Roorkee.
Funding
This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2023, LA/P/0068/2020 e UID/50019/2025 https://doi.org/10.54499/LA/P/0068/2020) and https://doi.org/10.54499/UID/PRR/50019/2025. M.O. Molina was supported by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) through the DRI/India/0098/2020 project (https://doi.org/10.54499/DRI/India/0098/2020), the Instituto Dom Luiz through the UID/PRR/50019/2025 (https://doi.org/10.54499/UID/PRR/50019/2025), and by the Horizon Europe research and innovation programs under grant agreement no. 101081661 (WorldTrans). AA extends thanks to the Anusandhan National Research Foundation for the research grant (CRG/2023/003449) facilitated at IIT Roorkee.
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M.O. Molina contributed in the conceptualization, methodology, formal analysis, writing and discussion.PM Soares and R. Trigo contributed in the conceptualization, methodology, writing and discussion.AA contributed in the methodology, writing and discussion.
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Molina, M.O., Soares, P.M.M., Agarwal, A. et al. Emerging heat stress patterns across India under future climate scenarios. Sci Rep (2026). https://doi.org/10.1038/s41598-026-36299-3
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DOI: https://doi.org/10.1038/s41598-026-36299-3