This study explores the correlation of contaminants of emerging concern (CECs) in wastewater effluents using liquid chromatography (LC), supercritical fluid chromatography (SFC), and comprehensive two-dimensional gas chromatography (GC × GC) with derivatization, all coupled to high-resolution mass spectrometry (HRMS). Over 300 compounds, including frequently overlooked highly polar and nonpharmaceutical CECs, were identified. Monitoring programs mainly focus on reducing variability and assessing pollution in wastewater treatment plant (WWTP) effluents under dry weather conditions, often neglecting wet-weather discharges. In this study, correlation analysis revealed the complex impact of rainfall on wastewater effluent composition, identifying clusters of CECs introduced through rain runoff and discharges from retention basins. Rain events affected the removal efficiency of easily degradable CECs, with variations between WWTPs. Persistent compounds such as PFAS demonstrated strong intragroup correlations, reflecting their common sources and environmental stability. These findings provide valuable insights into the diverse profiles of CECs in wastewater and demonstrate the potential of correlation-based approaches to optimize treatment strategies to the specific challenges of individual WWTPs.