Auroras lighting up night skies across the United States are becoming a free, multi-day music festival for the eyes, likely to return Saturday and Sunday, and possibly into next week, federal forecasters said.

In addition to the U.S., there have reports of sightings in Germany, Switzerland, China, England and Spain. The timing is not bad for viewers, although aurora spotters may have to be up at last call to get the best look.

National Oceanic and Atmospheric Administration forecasters say the…