Floating nuclear power stations (FNPSs) are being constantly developed due to their potential for broad application. Meteorological parameters are an important basis for heating, ventilation and air conditioning (HVAC) system design and energy estimation. However, existing HVAC meteorological parameters are mostly applicable to inland buildings and are becoming obsolete due to climate change. This paper aims to determine the outdoor design temperature and relative humidity for FNPSs. Raw weather data recorded over a 30-year period from National Oceanic and Atmospheric Administration (NOAA) were used. Considering nuclear safety requirements and energy conservation goals, the HVAC meteorological parameters are classified into safety class parameters for nuclear safety-related systems and non-safety class parameters for conventional systems. In addition, the area of China Sea and its vicinity is subdivided into 18 sea regions to reflect local climate characteristics. For a typical FNPS, the outdoor design temperature proposed is compared with that provided in several standards from the perspective of cooling/heating load. It shows that cooling and heating loads with safety class design temperature are 34.0% and 26.5% less than the maximum design cooling and heating loads, respectively. This study can serve as a reference for the determination of HVAC meteorological parameters of FNPSs.