This study explores the microphysical and thermodynamic influences on rain evaporation in the sub-cloud layer over Barbados from January to November 2020. The findings reveal that microphysical properties, namely geometric mean diameter (Dg,cb) and raindrop concentration, dominate evaporation processes, while thermodynamic factors like cloud base height and surface relative humidity have smaller impact due to their limited variability. A radar and a 1-D model analysis shows that smaller Dg,cb leads to rapid increases in rain evaporation fraction (REF), as smaller drops evaporate completely. In contrast, larger Dg,cb results in slower evaporation and more gradual REF changes. Weak rain cases, occurring more frequently, reduces the mean evaporation flux (Fe), while intense rain, despite being less common, significantly enhances Fe due to the greater mass of evaporated rain. These results emphasize the pivotal role of microphysical variability in driving rain evaporation and shaping its vertical structure in the trade wind cumulus environment.