After a spectacular appearance on Thursday evening, the Northern Lights could be visible again in parts of the USA. So where can you see them?

A “severe” geomagnetic storm warning is again in effect for Friday, according to the Space Weather Prediction Center and the National Oceanic and Atmosphere Administration. The same watch was also in effect for Thursday, resulting in the Northern Lights being seen much further south than usual.

“Watches of this level are very rare,” the agency said.

However, the line where the lights could be seen has shifted.

Where can you see the Northern Lights on Friday?

Friday's aurora forecast shows the observation occurring just over the Chicago area and approaching the Illinois-Wisconsin state line.

The latest update comes after an evening in which lights were visible across much of the Chicago area on Thursday.

Here is the most current map from the Space Prediction Center as of midday Friday:

What are the Northern Lights and what causes them?

The northern lights are amplified when coronal mass ejections (CMEs) erupt from the sun and race through space before hitting Earth's atmosphere. According to SWPC, CMEs are “large explosions of plasma and magnetized particles from the solar corona.”

These ejections increase in size as they approach Earth's atmosphere and can trigger geomagnetic storms when they arrive.

According to SWPC, auroras can be seen shortly after sunset or before sunrise. They are not visible during the day and do not need to be directly overhead to be seen, provided conditions are bright enough.

“For many people, the Northern Lights are a beautiful nighttime phenomenon that is worth traveling to Arctic regions to observe,” the SWPC said. “For most people, it’s the only way to actually experience space weather.”

Northern lights in the Chicago area

Luckily, much of the northern half of the U.S. didn't have to travel far to see them on Thursday.

Although the lights are visible to the naked eye, images taken with digital cameras may make auroras more visible.

If you didn't get a chance to look up on Thursday, or you're unable to go outside on Friday evening, here's a look back at the Northern Lights that were visible over the Chicago area last night.