Hot weather and heat extremes are increasingly prevalent in recent years. Urban redevelopment offers a great opportunity to reshape our neighborhoods and enhance climate resilience of our cities. In Hong Kong, plot ratio transfer was introduced in redevelopment projects to reorganize the building volume and free up some land for green spaces. With such a new planning mechanism, building coverage, building geometry, and green spaces are interacting elements in the planning system. A dynamic model is required to formulate planning strategies for heat mitigation in core urban areas. This study will take the Yau-Tsim-Mong area in Hong Kong as a typical case for climate responsive redevelopment strategies in high-density areas. With microclimate modeling, this study will first identify climate sensitive areas in the district, such as waterfront and wind paths. Based on the assessment results, different redevelopment scenarios will be tested with parametric studies: (a) highly sensitive areas with reduced building density, and increased building density in areas with low climate sensitivity with transfer plot ratio; (b) planning of green spaces for optimized cooling outcomes. The simulation will be conducted in both prevailing summer weather type and extreme hot weather. The synergetic effects between building geometry and urban greenery in heat mitigation will be explored with a dynamic model. The study will reveal planning elements that affect climate sensitivity and the thermal environments in high-density urban areas. Climate responsive planning strategies for redeveloping high-density core urban areas will be summarized. The study will also offer design recommendation for green space planning as a heat mitigation approach in different redevelopment scenarios.