Urban environments lie at the confluence of social, cultural, and economic activities and have unique biophysical characteristics due to continued infrastructure development that generally replaces natural landscapes with built-up structures. The vast majority of studies on urban perturbation of local weather and climate have been centered on the urban heat island (UHI) effect, referring to the higher temperature in cities compared to their natural surroundings. Besides the UHI effect and heat waves, urbanization also impacts atmospheric moisture, wind, boundary layer structure, cloud formation, dispersion of air pollutants, precipitation, and storms. In this overview talk, we will first briefly introduce the datasets and methods used in studying urban areas and their impacts through both observation and modeling. Then we will highlight a few recent studies using the latest Weather Research and Forecasting model coupled with the different versions of urban models and summarize the scientific insights on the impact of urbanization on various aspects of regional climate and extreme weather. We find UHI tends to get stronger on hotter summer nights, especially over warmer South. Heat related human discomfort exposure increases by 3–5 hour per day due to urbanization. We analyze the opposite impacts of urbanization and irrigation on convective environment and precipitation. We also conduct a series of sensitivity experiments to isolate the influence of lake breeze and urbanization to investigate the contrasting effects from urbanization and lake breeze on summer heat stress over Chicago metropolitan area (CMA). Our modeling results suggest the intensification of heat stress over CMA by urbanization is 1.5-2 times greater than the reduction by the lake breeze during late afternoon to evening. We also simulate and compare the impact of different roofing mitigation strategies (solar panel, cool and green roof) on heat stress and energy consumption over CMA. Finally, we will summarize the major research gaps and challenges in our understanding of the impacts of urbanization and provide our perspective and recommendations for future research priorities and directions.