Site characterization studies have identified Lenghu site as a world-class location for optical-infrared astronomy owing to exceptional atmospheric conditions. The spatial distribution of precipitable water vapor (PWV) and its altitudinal variations are crucial for observatory siting strategies. Utilizing multi-year meteorological data from five high-elevation weather stations (3311–4200 m), this study quantifies key spatiotemporal variations in PWV. Our analysis indicates a clear trend of decreasing PWV with increasing elevation across all times of day, with the frequency of sub-2 mm events at night rising from 44.59% at 3311 m to 53.63% at 4200 m, suggesting improved suitability of these sites for infrared-to-submillimeter observations. Pronounced seasonality manifests as consistent summer maxima and winter minima across altitudes, with the 4200 m site exhibiting notably arid winters averaging 0.91 mm contrasting with summer means of 7.03 mm. These findings establish an essential reference for altitudinal optimization of next-generation astronomical facilities at Lenghu.