On 2 March 2025, an extreme rain-to-snow weather event occurred in Shandong, with daily precipitation at 53 meteorological stations exceeding the historical records in March. Based on data of vertical detection networks and meteorological stations as well as ERA5 data, this study analyzes the microphysical parameter characteristics of hydrometeor particles during the event’s phase transition and summarizes the monitoring indicators using novel detection data. The results are as follows. (1) The synoptic system of the event is the Jianghuai cyclone. During the initial rainfall stage, the primary synoptic systems are upper-level trough, shear line and surface inverted trough. After it turns to easterly winds in the lower troposphere, the temperature decreases, the precipitation phase changes from rain to sleet or ice particles, and finally to pure snow. The circulation during the pure snow stage is a backflow pattern, with a cold pad in the lower troposphere and warm and humid air climbing along the cold pad in the middle and upper troposphere. When the cold pad thickens to nearly 5 km, the snowfall ends. (2) During the rainfall stage, a melting layer exists near 2 km altitude. Below this layer, the radial velocity is generally above 5 m·s^-1. As the radial velocity gradually decreases, the phase transforms into sleet or ice particles. When the radial velocity drops below 2 m·s^-1, the precipitation becomes pure snow. Notably, the melting layer abruptly decreases to the surface during the rain-to-snow transition, linked to the intensity of near-surface cold air intrusion, and it can be observed by dual-polarization radar, millimeter wave cloud measuring instrument and wind profile radar. Heavy snowfall stage normally corresponds to high Z_H values and low Z_DR values below 1 km. (3) When the precipitation phase is rain, ice particles or sleet, the joint distribution patterns of particle diameter and terminal fall velocity are similar, all approximating the empirical relationship of raindrops. After the precipitation transitions to pure snow, the particle size spectrum broadens, the particle diameter reaches its maximum, and the terminal fall velocities of most particles concentrate below 4 m·s^-1. Precipitation intensity could be determined by particle concentration, spectral width and Z_H.