This dataset contains long-term mean monthly values of key meteorological and hydrological parameters for the Lake Chimaditida area, Western Macedonia, Greece. The dataset covers 7 parameters presented as monthly climatological averages across 12 months: air temperature (°C), precipitation (mm), evapotranspiration (mm), solar radiation Rs (W/m²), wind speed (m/s), lake surface elevation (m a.s.l.), and runoff volume. The data are intended for use in water balance modelling, climate characterisation, and hydrological studies of the Chimaditida wetland catchment.