Abstract: This study examines the structural characteristics, diurnal variations, and formation mechanisms of low-level jets (LLJs) along the west coast of the Guangdong Province, South China, using wind-profile radar observations, automatic weather station precipitation data, and ERA5 reanalysis data from the region's first rainy season (2014–2016). The effects of LLJs of varying intensities on the temporal and spatial distribution of orographic precipitation in three key regions of Guangdong are also discussed. Key findings include: (1) the cumulative occurrence probability of LLJs is 21.2%, with most jets falling into class 1–3 categories. Approximately 77.1% of LLJs exhibit wind speeds below 14 m·s⁻¹, and 84.7% have southwest southwesterly winds. Most of the vertical shear of wind speed below the maximum wind speed of LLJ ranges between 5 and 25 × 10⁻³s⁻¹. The height of the maximum wind speed shows a bimodal distribution, primarily appearing within 1 km in the boundary layer. (2) Synoptic-system-related LLJs (SLLJs) peak at night, while the boundary layer jets (BLJs) exhibit double peaks in the early morning and afternoon. Nocturnal BLJ peaks are driven by inertial oscillations linked to local land-sea breeze circulation. The pressure difference between the low latitude Asian continental low pressure and the Northwest Pacific Ocean high pressure near the surface, plays a key role in the formation of BLJs with different intensities. The development of daytime continental low pressure is the primary driver of the afternoon peak in strong BLJs. (3) The impact of BLJs on the distribution and intensity of orographic precipitation in the Guangdong Province is complex. Orographic precipitation on large-scale windward slopes dominates northern central inland regions and eastern coastal areas of Guangdong. Stronger BLJs lead to more intense orographic precipitation. While heavy orographic precipitation along the east coast of Guangdong remains stable, inland orographic precipitation centers in northern central Guangdong shift northwest as BLJs intensify. In the west coastal areas of Guangdong, windward and downwind slopes of medium- and small-scale mountains, as well as lee-side wake convergence areas, generate significant orographic precipitation. However, intense orographic precipitation only occurs with adequate low-level inflow wind speed. (4) Under varying BLJ intensities, orographic precipitation in inland central and northern Guangdong exhibits a bimodal pattern, peaking in the morning and afternoon. The afternoon peak is about twice as intense as the morning peak, and both peaks increase in intensity as BLJs strengthen. With stronger BLJs, the diurnal bimodal pattern evolves into a trimodal structure in eastern coastal Guangdong Province. On the west coast, precipitation follows a bimodal or trimodal pattern under weak or strong jets, respectively. Under the influence of class 3 BLJ, a single-peak pattern is observed at noon.