The forecast looked promising for the northern lights to be visible across much of the United States on Sunday night.

From Michigan to Washington State and as far south as Alabama, people expected to be able to look up and see a light show, according to data from the National Oceanic and Atmospheric Administration.

But the geomagnetic storm that was expected to make the lights visible across such a wide swath of the country weakened, and instead of a light show, many got a lesson in how storms can change course.

Sometimes the storms come as predicted, and sometimes the forecast changes.

What happened on Sunday night?

The northern lights display, also known as the aurora borealis, is set off by geomagnetic storms, which are caused by coronal mass ejections, or eruptions of materials on the sun’s surface. On Sunday morning, the storm forecast for Sunday night was rated as severe enough for people to start chasing the aurora borealis.

Some people in northern Europe, Wyoming and Canada did report seeing the northern lights on Sunday night. But the storm weakened, disappointing people elsewhere who had hoped to see a show.

The magnetic orientation of a geomagnetic storm can change “in a minute’s notice,” and the energy transfer can become less efficient, said Lt. Cmdr. Bryan R. Brasher, a project manager at the Space Weather Prediction Center at NOAA.