Abstract Organized convective systems produce a disproportionate fraction of warm‐season rainfall, yet satellite‐based analyses generally neglect propagation‐relative microphysical organization. We develop a propagation‐relative partitioning framework using FY‐4A geostationary satellite observations to characterize sector‐resolved cloud effective radius–temperature profiles for 162 eastward‐propagating convective systems over China. Results reveal pronounced horizontal and vertical heterogeneity: the frontal sector sustains a deep warm‐rain growth layer, while the rear sector exhibits larger glaciated particles at colder temperatures. Prior to surface rainfall intensification, these profiles evolve from near‐monotonic growth to a distinct unimodal structure with strengthening frontal‐to‐rear contrasts. These findings identify propagation‐relative microphysical organization as an observational precursor to rainfall intensification in propagating convective systems.