Heat Stress in Iranian Cities (1992-2022): A Spatiotemporal Analysis of WBGT and UTCI indices
Abstract
Background:
Climate change is accelerating heat stress globally, especially in Iran's arid and semi-arid regions, threatening public and occupational health. Since air temperature alone poorly reflects physiological stress, this study used WBGT and UTCI to examine long-term spatiotemporal trends across ten diverse Iranian cities.
Methods:
Using daily meteorological data from the Global Surface Summary of the Day (GSOD), we calculated WBGT using the Liljegren model and UTCI using the UTCI-Fiala model. Descriptive statistics and linear regression analyses were conducted in Microsoft Excel to assess annual trends in average and maximum WBGT and UTCI values.
Results:
The analysis revealed clear spatial and temporal variations in WBGT and UTCI across Iranian cities from 1992 to 2023. Southern cities such as Bandar Abbas and Ahvaz recorded the highest average WBGT (23.46°C and 19.46°C) and UTCI (28.61°C and 25.84°C), with Ahvaz showing the highest maximum UTCI (51.68°C). Significant upward trends in both average and maximum WBGT and UTCI were observed in most cities (p < 0.001), particularly in Ahvaz (WBGT slope = 0.50, UTCI = 0.75). These findings indicate intensifying chronic and extreme heat stress across diverse climatic zones in Iran.
Conclusion:
This study found rising WBGT and UTCI trends across Iranian cities, indicating growing heat stress risks. Southern cities face extreme conditions, but increases are nationwide, highlighting urgent needs for heat adaptation strategies in public health, labor safety, and urban planning.
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15. Heidari H, Golbabaei F, Shamsipour A, Rahimi Forushani A, Gaeini A. Outdoor occupational environments and heat stress in IRAN. J Environ Health Sci Eng. 2015;13:48.
16. Gauer R, Meyers BK. Heat-Related Illnesses. Am Fam Physician. 2019;99(8):482-9.
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18. Golbabaei F, Asour AA, Keyvani S, Kolahdouzi M, Mohammadiyan M, RAMANDI FF. Limitations of WBGT Index for Application in Industries: A Systematic Review. International Journal of Occupational Hygiene. 2021.
19. Mohammadi M, Khoorani A. Spatiotemproal changes and hot spots of UTCI index over Iran. Urban Climate. 2024;56:102031.
20. Kjellstrom T, Briggs D, Freyberg C, Lemke B, Otto M, Hyatt O. Heat, Human Performance, and Occupational Health: A Key Issue for the Assessment of Global Climate Change Impacts. Annu Rev Public Health. 2016;37:97-112.
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22. Liljegren JC, Carhart RA, Lawday P, Tschopp S, Sharp R. Modeling the wet bulb globe temperature using standard meteorological measurements. J Occup Environ Hyg. 2008;5(10):645-55.
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24. Chaparinia F, Hadei M, Yaghmaeian K, Hadi M, Naddafi K. Evaluation of climate indices related to water resources in Iran over the past 3 decades. Scientific Reports. 2025;15(1):11846.
25. Rajeswari JR, Fountoukis C, Siddique A, Moosakutty S, Mohieldeen Y, Ayoub MA, et al. Urban heat island phenomenon in a desert, coastal city: The impact of urbanization. Urban Climate. 2024;56:102016.
26. Gharaee M, Zeraati H, Sadeghi A, Karimi S, Hadei M. Trends and Variability in Diurnal Temperature Range (DTR) in Khuzestan Province (1990-2022). Health in Emergencies and Disasters Quarterly. 2025;11(1):0-.
27. Hadei M, Hopke PK, Aghababaeian H, Faridi S, Hasham Firooz M, Ostadtaghizadeh A. Association of heat and cold waves with cause-specific mortality in Iran: a systematic review and meta-analysis. Scientific Reports. 2024;14(1):23327.
28. Parsons K. Human Thermal Environments: The Effects of Hot, Moderate, and Cold Environments on Human Health, Comfort, and Performance, Third Edition2014. 1-586 p.
29. Ou Y, Wang F, Zhao J, Deng Q. Risk of heatstroke in healthy elderly during heatwaves: A thermoregulatory modeling study. Building and Environment. 2023;237:110324.
30. Isaac T, Ranjith S, Latha PK, Shanmugam R, Venugopal V. Physiological strain in outdoor workers: The hidden danger of high humidity. Environmental Research. 2025;276:121495.
31. Vatani J, Golbabaei F, Dehghan SF, Yousefi A. Applicability of Universal Thermal Climate Index (UTCI) in occupational heat stress assessment: a case study in brick industries. Ind Health. 2016;54(1):14-9.
32. Broomandi P, Satyanaga A, Bagheri M, Hadei M, Galán-Madruga D, Fard AM, et al. Extreme Temperature Events in Kazakhstan and Their Impacts on Public Health and Energy Demand. Global Challenges. 2025;9(2):2400207.
33. Blazejczyk K, Jendritzky G, Bröde P, Baranowski J, Fiala D, bullet G, et al. An introduction to the Universal Thermal Climate Index (UTCI). Geographia Polonica. 2013;86:5-10.
34. Magdy Hamed M, Alasow A, Shahid S. Global Trends in Human Thermal Stress: A Spatiotemporal Analysis from 1940 to 2020. Earth Systems and Environment. 2024.
35. Yang Z, Peng J, Liu Y, Jiang S, Cheng X, Liu X, et al. GloUTCI-M: a global monthly 1 km Universal Thermal Climate Index dataset from 2000 to 2022. Earth Syst Sci Data. 2024;16(5):2407-24.
36. Ding X, Zhao Y, Strebel D, Fan Y, Ge J, Carmeliet J. A Wrf-Ucm-Solweig Framework of 10m Resolution to Quantify the Intra-Day Impact of Urban Features on Thermal Comfort2023.
37. Zare S, Shirvan HE, Hemmatjo R, Nadri F, Jahani Y, Jamshidzadeh K, et al. A comparison of the correlation between heat stress indices (UTCI, WBGT, WBDT, TSI) and physiological parameters of workers in Iran. Weather and Climate Extremes. 2019;26:100213.
38. Kyaw A, Magdy Hamed M, Shahid S. Spatiotemporal changes in Universal Thermal Climate Index over South Asia. Atmospheric Research. 2023;291:106838.
39. Kadkhoda E, Omidvar K, Zarrin A, Mazidi A. Seasonal analysis and trend of heat stress in Iran using ERA5 data. Journal of the Earth and Space Physics. 2023.
40. Sherwood SC, Huber M. An adaptability limit to climate change due to heat stress. Proceedings of the national academy of sciences. 2010;107(21):9552-5.
2. Romanello M, Napoli Cd, Green C, Kennard H, Lampard P, Scamman D, et al. The 2023 report of the Lancet Countdown on health and climate change: the imperative for a health-centred response in a world facing irreversible harms. The Lancet. 2023;402(10419):2346-94.
3. Lemke B, Kjellstrom T. Calculating workplace WBGT from meteorological data: a tool for climate change assessment. Ind Health. 2012;50(4):267-78.
4. Blazejczyk K, Epstein Y, Jendritzky G, Staiger H, Tinz B. Comparison of UTCI to selected thermal indices. International Journal of Biometeorology. 2012;56(3):515-35.
5. Bröde P, Fiala D, Błażejczyk K, Holmér I, Jendritzky G, Kampmann B, et al. Deriving the operational procedure for the Universal Thermal Climate Index (UTCI). International Journal of Biometeorology. 2012;56(3):481-94.
6. Kovats RS, Hajat S. Heat stress and public health: a critical review. Annu Rev Public Health. 2008;29:41-55.
7. Kjellstrom T, Freyberg C, Lemke B, Otto M, Briggs D. Estimating population heat exposure and impacts on working people in conjunction with climate change. Int J Biometeorol. 2018;62(3):291-306.
8. Raziei T. Köppen-Geiger climate classification of Iran and investigation of its changes during 20th century. Journal of the Earth and Space Physics. 2017;43(2):419-39.
9. amar. Population and Housing Census 2023 [
10. Tabari H, Somee BS, Zadeh MR. Testing for long-term trends in climatic variables in Iran. Atmospheric Research. 2011;100(1):132-40.
11. Yazdanpanah H, Eitzinger J, Baldi M. Analysis of the extreme heat events in Iran. International Journal of Climate Change Strategies and Management. 2017;9:00-.
12. Kiarsi M, Amiresmaili M, Mahmoodi M, Farahmandnia H, Nakhaee N, Zareiyan A, et al. Heat wave adaptation paradigm and adaptation strategies of community: A qualitative phenomenological study in Iran. Journal of education and health promotion. 2022;11(1):408.
13. Zittis G, Hadjinicolaou P, Almazroui M, Bucchignani E, Driouech F, El Rhaz K, et al. Business-as-usual will lead to super and ultra-extreme heatwaves in the Middle East and North Africa. npj Climate and Atmospheric Science. 2021;4(1):20.
14. Krishnamurthy M, Ramalingam P, Perumal K, Kamalakannan LP, Chinnadurai J, Shanmugam R, et al. Occupational Heat Stress Impacts on Health and Productivity in a Steel Industry in Southern India. Safety and Health at Work. 2017;8(1):99-104.
15. Heidari H, Golbabaei F, Shamsipour A, Rahimi Forushani A, Gaeini A. Outdoor occupational environments and heat stress in IRAN. J Environ Health Sci Eng. 2015;13:48.
16. Gauer R, Meyers BK. Heat-Related Illnesses. Am Fam Physician. 2019;99(8):482-9.
17. Di Napoli C, Barnard C, Prudhomme C, Cloke HL, Pappenberger F. ERA5‐HEAT: A global gridded historical dataset of human thermal comfort indices from climate reanalysis. Geoscience data journal. 2021;8(1):2-10.
18. Golbabaei F, Asour AA, Keyvani S, Kolahdouzi M, Mohammadiyan M, RAMANDI FF. Limitations of WBGT Index for Application in Industries: A Systematic Review. International Journal of Occupational Hygiene. 2021.
19. Mohammadi M, Khoorani A. Spatiotemproal changes and hot spots of UTCI index over Iran. Urban Climate. 2024;56:102031.
20. Kjellstrom T, Briggs D, Freyberg C, Lemke B, Otto M, Hyatt O. Heat, Human Performance, and Occupational Health: A Key Issue for the Assessment of Global Climate Change Impacts. Annu Rev Public Health. 2016;37:97-112.
21. Mora C, Dousset B, Caldwell IR, Powell FE, Geronimo RC, Bielecki Coral R, et al. Global risk of deadly heat. Nature Climate Change. 2017;7(7):501-6.
22. Liljegren JC, Carhart RA, Lawday P, Tschopp S, Sharp R. Modeling the wet bulb globe temperature using standard meteorological measurements. J Occup Environ Hyg. 2008;5(10):645-55.
23. Fallah Ghalhari G, Farhang Dehghan S, Akhlaghi Pirposhteh E, Asghari M. Trend Analysis and Temporal and Spatial Distribution of Wet Bulb Globe Temperature as a Heat Stress Index in Iran during the Summer Season over a 30-Year Period. ssu-jehsd. 2021;6(4):1476.
24. Chaparinia F, Hadei M, Yaghmaeian K, Hadi M, Naddafi K. Evaluation of climate indices related to water resources in Iran over the past 3 decades. Scientific Reports. 2025;15(1):11846.
25. Rajeswari JR, Fountoukis C, Siddique A, Moosakutty S, Mohieldeen Y, Ayoub MA, et al. Urban heat island phenomenon in a desert, coastal city: The impact of urbanization. Urban Climate. 2024;56:102016.
26. Gharaee M, Zeraati H, Sadeghi A, Karimi S, Hadei M. Trends and Variability in Diurnal Temperature Range (DTR) in Khuzestan Province (1990-2022). Health in Emergencies and Disasters Quarterly. 2025;11(1):0-.
27. Hadei M, Hopke PK, Aghababaeian H, Faridi S, Hasham Firooz M, Ostadtaghizadeh A. Association of heat and cold waves with cause-specific mortality in Iran: a systematic review and meta-analysis. Scientific Reports. 2024;14(1):23327.
28. Parsons K. Human Thermal Environments: The Effects of Hot, Moderate, and Cold Environments on Human Health, Comfort, and Performance, Third Edition2014. 1-586 p.
29. Ou Y, Wang F, Zhao J, Deng Q. Risk of heatstroke in healthy elderly during heatwaves: A thermoregulatory modeling study. Building and Environment. 2023;237:110324.
30. Isaac T, Ranjith S, Latha PK, Shanmugam R, Venugopal V. Physiological strain in outdoor workers: The hidden danger of high humidity. Environmental Research. 2025;276:121495.
31. Vatani J, Golbabaei F, Dehghan SF, Yousefi A. Applicability of Universal Thermal Climate Index (UTCI) in occupational heat stress assessment: a case study in brick industries. Ind Health. 2016;54(1):14-9.
32. Broomandi P, Satyanaga A, Bagheri M, Hadei M, Galán-Madruga D, Fard AM, et al. Extreme Temperature Events in Kazakhstan and Their Impacts on Public Health and Energy Demand. Global Challenges. 2025;9(2):2400207.
33. Blazejczyk K, Jendritzky G, Bröde P, Baranowski J, Fiala D, bullet G, et al. An introduction to the Universal Thermal Climate Index (UTCI). Geographia Polonica. 2013;86:5-10.
34. Magdy Hamed M, Alasow A, Shahid S. Global Trends in Human Thermal Stress: A Spatiotemporal Analysis from 1940 to 2020. Earth Systems and Environment. 2024.
35. Yang Z, Peng J, Liu Y, Jiang S, Cheng X, Liu X, et al. GloUTCI-M: a global monthly 1 km Universal Thermal Climate Index dataset from 2000 to 2022. Earth Syst Sci Data. 2024;16(5):2407-24.
36. Ding X, Zhao Y, Strebel D, Fan Y, Ge J, Carmeliet J. A Wrf-Ucm-Solweig Framework of 10m Resolution to Quantify the Intra-Day Impact of Urban Features on Thermal Comfort2023.
37. Zare S, Shirvan HE, Hemmatjo R, Nadri F, Jahani Y, Jamshidzadeh K, et al. A comparison of the correlation between heat stress indices (UTCI, WBGT, WBDT, TSI) and physiological parameters of workers in Iran. Weather and Climate Extremes. 2019;26:100213.
38. Kyaw A, Magdy Hamed M, Shahid S. Spatiotemporal changes in Universal Thermal Climate Index over South Asia. Atmospheric Research. 2023;291:106838.
39. Kadkhoda E, Omidvar K, Zarrin A, Mazidi A. Seasonal analysis and trend of heat stress in Iran using ERA5 data. Journal of the Earth and Space Physics. 2023.
40. Sherwood SC, Huber M. An adaptability limit to climate change due to heat stress. Proceedings of the national academy of sciences. 2010;107(21):9552-5.
| Files | ||
| Issue | Vol 1 No 1 (2026): Winter 2026 | |
| Section | Articles | |
| Keywords | ||
| Iran Extreme Heat Climate Change Global Warming Public Health | ||
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How to Cite
1.
Gharaee M, Shoja E, Rahmatinia M, Hadei M. Heat Stress in Iranian Cities (1992-2022): A Spatiotemporal Analysis of WBGT and UTCI indices. CHJ. 2025;1(1):24-31.
