We used a three-year dataset from an impact disdrometer to study the diurnal to interannual variation of the raindrop size distribution (DSD) over Palau in the Western Pacific warm pool. The DSD variability was primarily seasonal, with a secondary contribution due to the El Niño Southern Oscillation (ENSO) cycle. We did not find evidence of a diurnal cycle. In the seasonal cycle, mean drop diameters tended to increase during the westerly monsoon period. Within this period, drop diameters generally increased during the El Niño year and decreased during the La Niña year. However, within the easterly monsoon period, they generally increased in the winter following La Niña, and decreased in the winter following El Niño. The amplitude of the seasonal variation in mean drop diameter was approximately the same as that in Singapore and Sumatra, and about one third of that in India.