ISSN: 2538-4384; Geographical Researches Quarterly Journal. 2018;33(3):38-57 C I T A T I O N L I N K S Copyright© 2018. This open-access article is published under the terms of the Creative Commons Attribution-NonCommercial 4.0 Interna- tional License which permits Share (copy and redistribute the material in any medium or format) and Adapt (remix, transform, and build upon the material) under the Attribution-NonCommercial terms. Climate Change Impact Assessment on Outdoor Thermal Comfort Changes Using Physiological Equivalent Temperature (PET) Index in Mashhad [Akbari & Konopacki; 2004] Energy effects of heat-island ...; [Ali-Toudert; 2005] Dependence of outdoor thermal comfort ...; [Analitis, et al.; 2008] Effects of cold weather on mortality ...; [ASHRAE; 2009] Fundamentals, American society of ...; [ASHRAE; 2004] Fundamentals, American society of ...; [Cheung & Hart; 2014] Climate change and thermal comfort ...; [Cimellaro; 2016] Urban resilience for emergency ...; [Dai; 2014] The impact of urban form on thermal ...; [Djongyang, et al; 2010] Thermal comfort ...; [Draper & Richards; 2009] Dictionary for managing trees in ...; [Ebrahimzadeh & Esmaeil Negad; 2017] The future challenge of climatic refugees regional ...; [Erell, et al; 2010] Urban microclimate: Designing the ...; [Fallah Ghalhari, et al; 2016] Assessing the seasonal variability of thermal ...; [Fanger; 1970] Thermal comfort: Analysis and applications ...; [Hajat, et al.; 2006] Impact of high temperatures on mortality ...; [Hansen et al.; 2008] The effect of heat waves on mental ...; [Heidari & Monam; 2013] Evaluation of thermal comfort indices in ...; [Hensel; 1981] Thermoreception and Temperature ...; [Höppe; 2002] Different aspects of assessing indoor ...; [IPCC; 2007] Climate change synthesis report - summary ...; [Johansson; 2006] Influence of urban geometry on outdoor ...; [Karimian; 2013] Optimization of urban green space for the ...; [Linares & Dı´az; 2008] Impact of high temperatures on hospital ...; [Matzarakis, et al.; 2002] Radiation and thermal ...; [Matzarakis, et al.; 2010] Modelling radiation fluxes in simple ...; [Monsefi Parapari; 2015] Adaptation to climate change ...; [Morris; 2008] History of urban form ...; [Oliver; 2005] Encyclopedia of world ...; [Pirard et al.; 2005] Summary of the mortality...; [Prasad et al.; 2009] Climate resilient cities ...; [Qanbarzadeh & Behniafar; 2007] Fundemental of environmental ...; [Roaf, et al.; 2009] Adapting buildings and cities for ...; [Shams, et al.; 2014] Assessing climate conditions of Mashhad ...; [Szokolay; 2008] Architectural science the ...; [Taylor et al.; 2015] Mapping the effects of urban heat island ...; [Wilkinson; 2001] Cold comfort: The social and environmental ...; [Yang, Qet al.; 2016] Research on urban heat-island ...; [Yilmaz, et al.; 2013] The importance of thermal comfort in ...; [Yow; 2007] Urban heat Islands: Observations ...; [Zolfaghari; 2008] Determination of suitable calendar ... Introduction and Background In recent decades, increasing earth heat lead to the death of thosands of people in the world. This situation cause urban planning meet a major climate change challenges which needs to mitigate its effects. Increasing in population and various related activities in different fields has led to problems such as wave heat throughout the world. In addition, changing the pattern of these changes and their unpredictability has increased in cities, thus concern about reducing and adapting to these hazards in different dimensions lead to pay more attention to urban life and promoting human health. Aims The aim of this paper is to investigate effect of climate change which is caused by heat wave on outdoor thermal comfort in Mashhad city. Methodology Data collection method was based on library studies and also data gathered from meteorological station of Mashhad in the period of 10 years (2017-2007). The analysis method was based on Rayman and Excell software in Mashhad and physiological equivalent temperature (PET) index was the most commonly used index for evaluating outdoor thermal comfort. Conclusion Findings show that climate change and the effects of heat wave in Mashhad in July and August have affected the outdoor thermal comfort, which put human health at more risk in these months. Moreover, studies of outdoor thermal comfort changes in winter in this city shows that warming of these seasons experienced a rapid pace, so that over the past 10 years, outdoor thermal comfort has increased by +1.4°C in March, this number will reach 1.1+ in summer and July. Studies show that the summer and spring seasons of Mashhad are entering to the thermal stress range, while its cold seasons are becoming warmer and entering to outdoor thermal comfort range. A B S T R A C T A R T I C L E I N F O Article Type Original Research Authors Sanagar Darbani E. 1 MA, Rafieian M. 2 PhD, Hanaee T.* PhD, Monsefi Parapari D. 3 PhD Keywords Climate Change; Outdoor Thermal Comfort; physiological equivalent temperature(PET); Mashhad *Correspondence Address: Floor 1, NO. 19, Golestan Al- ley, Hashemieh 91.1, mashhad, Iran. Postal Code: 9178146713 Phone: - Fax: - Toktamhanaee@yahoo.com *Department of Urbanism, Mash- had Branch, Islamic Azad Univer- sity, Mashhad, Iran 1 Department of Urbanism, Mash- had Branch, Islamic Azad Univer- sity, Mashhad, Iran 2 Department of Urbanism, Faculty of Arts, Tarbiat Modares Univer- sity, Tehran, Iran 3 Department of Architecture, Fac- ulty of Architecture & Urbanism, Shahrood University Technology, Shahrood, Iran Article History Received: April 14, 2018 Accepted: August 21, 2018 ePublished: December 09, 2018 How to cite this article Sanagar Darbani E, Rafieian M, Hanaee T, Monsefi Parapari D. Climate Change Impact Assessm- ent on Outdoor Thermal Comfo- rt Changes Using Physiological Equivalent Temperature (PET) Index in Mashhad. Geographical Researches Quarterly Journal. 2018;33(3):38-57.