<jats:title>Abstract</jats:title><jats:p>Variations in oxygen isotope ratios (δ<jats:sup>18</jats:sup>O) measured from modern precipitation and geologic archives provide a promising tool for understanding modern and past climate dynamics and tracking elevation changes over geologic time. In areas of extreme topography, such as the Tibetan Plateau, the interpretation of δ<jats:sup>18</jats:sup>O has proven challenging. This study investigates the climate controls on temporal (daily and 6 h intervals) and spatial variations in present‐day precipitation δ<jats:sup>18</jats:sup>O (δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic>) across the Tibetan Plateau using a 30 year record produced from the European Centre/Hamburg ECHAM5‐wiso global atmospheric general circulation model (GCM). Results indicate spatial and temporal agreement between model‐predicted δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic> and observations. Large daily δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic> variations of −25 to +5‰ occur over the Tibetan Plateau throughout the 30 simulation years, along with interannual δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic> variations of ~2‰. Analysis of extreme daily δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic> indicates that extreme low values coincide with extreme highs in precipitation amount. During the summer, monsoon vapor transport from the north and southwest of the plateau generally corresponds with high δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic>, whereas vapor transport from the Indian Ocean corresponds with average to low δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic>. Thus, vapor source variations are one important cause of the spatial‐temporal differences in δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic>. Comparison of GCM and Rayleigh Distillation Model (RDM)‐predicted δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic> indicates a modest agreement for the Himalaya region (averaged over 86°–94°E), confirming application of the simpler RDM approach for estimating δ<jats:sup>18</jats:sup>O<jats:italic><jats:sub>p</jats:sub></jats:italic> lapse rates across Himalaya.</jats:p>