Reliable climate data are essential for environmental modelling, agriculture, hydrology, and climate-related analytics, yet observational datasets are often incomplete, restricted, or difficult to process. This paper presents CDSim, an open-source R package available on CRAN, designed to generate synthetic multi-station climate time series of temperature and rainfall. CDSim combines deterministic seasonal structure with stochastic variability to produce realistic monthly climate data across user-defined locations and time periods. The package supports reproducible simulation workflows, visualisation, and export to standard formats including CSV and NetCDF. CDSim is intended for reuse in education, workflow prototyping, benchmarking, and methodological development when observational climate data are unavailable or unsuitable.