Study region: The Yellow River Delta located in Shandong Province, northern China. Study focus: The contamination dynamics and potential sources of groundwater SO42- and NO3- are potentially affected by two worldwide issues: climate change-induced precipitation and seawater intrusion. This study investigated how seasonal precipitation and seawater intrusion impact SO42and NO3- in the coastal groundwater of the Yellow River Delta. New hydrological insights for the region: The results indicated significant degradation in the groundwater quality, with 95 % of the samples exceeding China's drinking water standard for SO42- (mean concentration: 829 mg/L), and 27 % exceeding the standard for NO3- (mean concentration: 55.0 mg/L). Health risk assessment confirmed nonnegligible noncarcinogenic risks, which were exacerbated by an arid climate. Notably, the risk was attributed primarily to overlooked SO42- rather than NO3- . Isotopic analysis using a Bayesian isotope mixing model revealed that SO42- was derived mainly from evaporite dissolution (47.3 f 19.7 %), followed by sewage (14.8 f 6.9 %) and seawater (12.3 f 3.9 %). This contamination was further promoted by seawater intrusion via stronger evaporite dissolution processes, particularly during the early rainy season. In contrast, NO3- was less sensitive to rainfall variation and seawater intrusion and was primarily affected by anthropogenic activities, including those related to sewage (57.9 f 10.9 %), soil nitrogen (29.0 f 8.7 %) and fertilizers (8.3 f 3.1 %). Our work confirmed that the flocculation of SO42- and NO3- in coastal groundwater is influenced by natural processes and surface anthropogenic activities driven by seasonal precipitation, more strongly affecting on SO42- than NO3- from seawater intrusion. The spatiotemporal findings establish a quantitative framework for managing vulnerable coastal groundwater systems in deltaic regions worldwide that face simultaneous challenges of seawater intrusion and anthropogenic pressure.