How to see the northern lights—and why they’re more common now

No matter how many times you see them, the northern lights, or aurora borealis—and their Southern Hemisphere equivalent, the aurora australis—are an ethereal, breathtaking sight. Dancing silently in Earth’s upper atmosphere, they form iridescent sheets of green and red (or sometimes blue and purple) light.

And tonight, across the northern United States—and even parts of the Midwest—they’re expected to put on a rare show.

Around mid-day on November 12 , coronal mass ejections (CMEs) are expected to reach Earth; as a result, when their electrically charged particles hit Earth’s atmosphere this week, states as far south as Illinois may be treated to vivid displays of northern lights. As many as 21 states —from Alaska and Montana to New England and New York—may experience colorful displa