Orbital-scale precipitation isotope records can elucidate climate forcing mechanisms and provide benchmarks for climate model validation. The ability to differentiate the influence of temperature, seasonality, and vapor transport history on precipitation isotope proxies is critical to both objectives. We present a 300 k.y. leaf wax hydrogen isotope record from the South China Sea with the effects of local condensation temperature removed (δ2Hwax–T). δ2Hwax–T reflects annually integrated precipitation δ2H in the Pearl River catchment of southeast China. Depleted δ2Hwax–T lags minimum precession (Pmin) by 1.0 ± 0.7 k.y., reflecting the influence of maximum summer insolation and minimum winter insolation, with a minor influence of global ice volume, which lags Pmin by 3.3 ± 0.4 k.y. In contrast, annually integrated cave δ18O minima in central China, 1000 km north of our site, lag Pmin by 2.7 ± 0.3 k.y., in phase with ice volume minima. This phase indicates that precipitation δ18O in central China is more strongly influenced by ice volume forcing at the precession band, with a lesser influence of Northern Hemisphere insolation. Our new δ2Hwax–T data demonstrate that precipitation isotopes in Asia have strong regional variability. Interpreting water isotope records within the context of regionally varying temperature, seasonality, and sensitivity to changing glacial boundary conditions is imperative to understanding Asian hydroclimatic change.