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Abstract Prolific winter (December‐January‐February) snowfall occurs over northwest Japan due to frequent sea‐effect precipitation that develops during cold‐air outbreaks over the Sea of Japan (SOJ). Knowledge of sea‐effect clouds and precipitation across the SOJ region has historically been constrained, however, by limited offshore in situ observations and remote‐sensing limitations. This paper uses sensors from National Aeronautics and Space Administration (NASA)'s A‐Train Satellite Constellation to examine winter sea‐effect properties in the SOJ region. The analysis shows that cloud and precipitation occurrence generally increases across the SOJ from Asia to Japan, as potential sea‐effect periods with an along‐orbit mean sea surface to 850‐hPa temperature difference ≥13 °C comprise a majority of the total clouds and precipitation. Sea‐effect clouds and precipitation occur most frequently in an arc‐shaped area that extends from the western SOJ, where the Japan‐Sea Polar‐Airmass Convergence Zone (JPCZ) is common, to the coast of Honshu, and then northward to Hokkaido. Radar, lidar, and column water path statistics along A‐Train orbital tracks show that sea‐effect precipitation is deepest along the central Honshu coast and becomes shallower but more frequent with northward extent. Precipitation amount and frequency maximize along the coast and adjacent mountains but decline with inland extent, most abruptly downstream of higher mountain barriers. This work illustrates that air‐sea interactions, coastal geometry, and regional topography strongly modulate cloud and precipitation patterns during sea‐effect periods in the SOJ region.