The microclimate of a dense urban environment is highly dependent on the form, structure, and material configuration of the buildings at the concerned site. In this study, we estimate the impact of urban characteristics on the micro-climatic condition of a district in a newly constructed city. Lusail is a new city which is being built just north of Doha, Qatar. The city buildings are required to be built with the local sustainability assessment tool called the Global Sustainability Assessment System (GSAS) kept in mind. A minimum GSAS 2 rating is required in all buildings. However, it is up to the contractors to further increase the sustainability perspectives of the building. To evaluate how variation in design characteristics affects the local microclimatic conditions and cooling loads, we assess the local conditions using the Urban Weather Generator and Openstudio simulation tools. Simulation results are obtained by varying the temporal distribution of two building types, i.e., mid-rise apartment and medium office. Results are shown through the Urban Heat Island Effect with temperature and humidity deviations revealing fluctuations in the microclimate. A diurnal behavior in temperatures can be seen compared to rural weather readings, with urban heat effect raising nighttime temperatures more than daytime temperatures with up to 1.3°C during one of Qatar's hottest days. The updated microclimate data are then further used in a residential building model in Openstudio and EnergyPlus to see the microclimate impacts in terms of cooling load requirements. An additional 4% (143100 kWh) cooling is needed in only one building of the Marina district, revealing a significant energy increase for the Marina district, which contains more than 100 buildings.