Wind turbines are exposed to rainfall, which has a long-term impact through erosion, and numerous studies have investigated the consequences of leading-edge erosion (LEE) on wind turbine blades. However, the potential effects of precipitation on turbine performance and on the experimental evolution of wakes have not yet been thoroughly analyzed. This paper presents a new methodology to study the impact of precipitation using experimental operational data. The methodology includes the necessary data processing, the definition of relevant meteorological parameters, and appropriate analysis methods. A commercial wind farm is evaluated following the proposed methodology, identifying differences in behavior between dry and rainy conditions at both the individual turbine level and the wind farm and wake levels, while accounting for the quantity and distribution of the available data.