A thunderstorm is like an orchestra where warm air rises, high-altitude winds lead the melody, and lightning punctuates the finale. But who decides where this orchestra will play? Scientists gathered 45 years of data and identified the chief conductor: El Niño, a warm current in the Pacific Ocean.

To hear the music of storms, they didn't chase every cloud. Instead, for each point on the planet they calculated two numbers: how much energy is available to lift the air, and how much the wind changes with height. Multiplying them together gave a "thunderstorm environment index." The threshold was tuned so that the number of storm days matched the actual lightning detected by sensors.

It turned out that El Niño controls thunderstorm hotspots over a quarter of the entire planet, and over more than half of the tropical oceans. Climate warming also adds storms: roughly 30 thunderstorm days per year for each degree of warming. But for now, this signal drowns in the usual weather variability, as storms fluctuate from year to year on their own.

Previously, it was unclear how strongly ocean currents influence thunderstorms and whether a warming signal could be detected. Now it's clear: El Niño is the chief conductor, while warming is still a quiet soloist. This knowledge could help provide early warnings of thunderstorm threats to farmers, power companies, and emergency services.