Extreme weather conditions, especially heatwave, are a threat to society, affecting livability, wellbeing, and social interactions. The present study aims to assess the monthly heat stress in the outdoor environment from 2010 to 2019 in Sonepat's municipality, representing a hot semi-arid climate. The authors applied three heat stress indices, namely, Wet bulb globe temperature (WBGT), Physiological equivalent temperature (PET), and Universal thermal climate index (UTCI), to estimate the grade of heat stress. While calculations, the highest average WBGT was found in July (33.4 +/- 0.77 degrees C), demonstrating July in the "Extreme heat stress" category. The highest mean PET was found in June (42.47 +/- 2.34 degrees C), indicating June in the "Extreme heat stress" category. The highest mean UTCI was found in June (38.58 +/- 1.82 degrees C), demonstrating "Very strong heat stress." The dry bulb temperature was found to be the most dominant parameter among meteorological parameters promoting extreme heat stress. It was concluded that extreme heat stress was observed in the Pre-monsoon hot weather season and summer monsoon season (especially in June), making the population vulnerable to mortality and morbidity. The findings could provide valuable information to people from various disciplines like Climate scientists, landscape designers, architects, and all relevant stakeholders to develop a heatwave action plan against adverse heat stress.(c) 2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the F-EIR Conference 2021 on Environment Concerns and its Remediation: Materials Science.