As a result of climate change and urbanization, rising temperatures are causing increasing concern about extreme heat in cities worldwide. Urban extreme heat like other climate-related phenomena is a complex problem that requires expertise from a range of disciplines and multi-faceted solutions. Therefore, this study aims to develop a comprehensive understanding of urban heat issue by taking a multi-level approach that integrates science, technology, and policy. Throughout the three main papers of this dissertation, a variety of quantitative and qualitative methods, such as microclimate modeling, machine learning, statistical analysis, and policy content analysis, are used to analyze urban heat from different perspectives. The first paper of this dissertation focuses on the street canyon scale, aiming to identify the physical and vegetation parameters that have the greatest impact on changing thermal conditions in urban environments and to understand how these parameters interact with each other. Moving towards identifying applicable heat-related data and measurement techniques, the second paper assesses whether lower-resolution temperature data and novel sources of vulnerability indicators can effectively explain intra-urban heat variations. Lastly, the third paper of this dissertation reviews heat-related plans and policies at the Planning Districts level in Virginia, providing insights into how extreme heat is framed and addressed at the regional and local levels. This analysis is particularly important for states such as Virginia, which historically have not experienced multiple days of extreme heat during summers, as is common in southern and southwestern states of the United States. The results of this study provide insights into the contributing and mitigating factors associated with extreme heat exposure, novel heat-related data and measurement techniques, and the types of analysis and information that should be included in local climate-related plans to better address extreme heat. This dissertation explores new avenues for measuring, understanding, and planning extreme heat in cities, thereby contributing to the advancement of knowledge in this field. / Doctor of Philosophy / Due to climate change and fast city growth, temperatures are rising, and extreme heat is becoming a big worry in cities worldwide. Urban extreme heat is a challenging problem that needs expertise from different majors and diverse solutions. This dissertation aims to understand urban heat better by integrating science, technology, and policy. The three main research papers of this dissertation use various methods like modeling, statistics, and policy analysis to study urban heat from different angles. The first paper focuses on city streets and how certain physical features and vegetation affect citizens' thermal comfort. The second paper explores new ways to measure heat in urban areas, including using new sources of data and the application of lower-resolution data. Finally, the third paper reviews heat-related plans and policies in Virginia, helping us understand how extreme heat is addressed in areas that might not be accustomed to high temperatures. This dissertation's findings provide useful insights into why the severity of extreme heat is not the same in different parts of cities, present new ways to measure this difference and find solutions to lessen the negative impacts of exposure to heat. It also shows what information needs to be included in plans and policies to better deal with extreme hot weather at the local level such as in towns and cities. By exploring new ways to understand and handle extreme heat in cities, this research helps make progress in this important field. The goal of this research is to help cities prepare for and cope with urban extreme heat, keeping people safe and creating sustainable cities for the future.