With the development of smart city initiatives, data fusion has become a key factor in enhancing urban governance capabilities. To further enable cross-domain data fusion and application, a meteorological data fusion framework based on the City Information Model (CIM) platform was proposed. The framework leverages the meteorological big data cloud platform to process multi-source heterogeneous data and utilizes the CIM platform to unify the spatiotemporal dimensions of cross-domain data, thereby constructing a multi-factor fusion analysis model. This model was tested and evaluated during the 2025 Chengdu World Games. The results demonstrate that it provides precise and efficient meteorological data support for diverse urban governance scenarios. It also addresses, to some extent, issues such as professional barriers and dimensional inconsistencies in the fusion of meteorological data with multi-domain data, significantly improving the precision of governance in megacities.