A telescope on the island of La Palma looked at the stars every clear night and recorded how much the air dimmed them. It's like photographing the same lightbulb every day and noticing that sometimes it shines more faintly because the room is dusty.

Scientists took thirty years of the telescope's records and found the nights when the light was dimmed especially strongly. Those were the dust arrivals. It turned out that in summer, dust arrives more often than at other times of the year. They also noticed that if winter brought unusual pressure patterns in one part of the Atlantic, and spring was dry in the Sahel, then summer would bring more dust.

Now, based on winter data, you can roughly predict what the dusty season will be like in summer. A telescope that measured stars has become a helper for meteorologists.