After a spectacular showing Thursday night, the Northern Lights could once again be visible in parts of the U.S. So, where can you see them?

According to the Space Weather Prediction Center and the National Oceanic and Atmosphere Administration, a "severe" geomagnetic storm watch is once again in effect for Friday. That same watch was in effect for Thursday, leading to the aurora being seen much further south than usual.

"Watches at this level are very rare," the agency said.

The line for where the lights could be seen, however, has shifted.

Where can you see the Northern Lights Friday

Friday's aurora forecast shows the viewing sitting just above the Chicago area, coming close to the Illinois-Wisconsin state line.

The latest update comes after an evening that saw the lights visible across a large portion of the Chicago area Thursday.

Here's the most recent map from the Space Prediction Center as of mid-day Friday:

What are the Northern Lights and what causes them?

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The Northern Lights are enhanced when coronal mass ejections, or CME’s, erupt from the sun and speed across space before hitting Earth’s atmosphere. According to the SWPC, CME’s are “large explosions of plasma and magnetized particles from the Sun’s corona.”

Those ejections expand in size as they approach Earth’s atmosphere, and can cause geomagnetic storms when they arrive.

According to the SWPC, auroras can be observed just after sunset or before sunrise. They are not visible during daytime hours, and do not need to be directly overhead to be seen, if conditions are bright enough.

"For many people, the aurora is a beautiful nighttime phenomenon that is worth traveling to arctic regions just to observe," the SWPC said. "It is the only way for most people to actually experience space weather."

Northern Lights in Chicago area

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

Though the lights may be visible with the naked eye, pictures taken with digital cameras may make auroras more visible.

If you didn't get a chance to look up Thursday, or you'll be unable to step outside Friday evening, here's a look back at the aurora visible across the Chicago area last night.