Near the island of New Guinea, thunderstorms and rain clouds often start over mountains in the afternoon and then move toward the coast. Surprisingly, many of these storms seem to “jump” across the shoreline and regenerate over the ocean at night, sometimes traveling hundreds of kilometers offshore. This study uses satellite rainfall data and specialized computer simulations to uncover how different “density currents” in the lower atmosphere—including daily winds flowing between land and sea (“land-sea breezes”) and cooler air spreading out from rainstorms (“cold pools”)—work together to push storms far into the ocean. During the daytime, cooler air from the sea breeze flows onshore until evening, creating a gap in the migrating storm. After sunset, the wind direction reverses, and a land breeze forms; if it merges with pockets of cool, rainy air, it can carry enough moisture out to sea to form new storms. Ocean waters that are relatively warm provide extra energy and moisture, further supporting overnight rainstorms far from land. Our findings help explain why some coastal areas experience heavy rain at odd hours and offer clues for improving weather and climate models in tropical regions, where accurate rainfall forecasts are critical.