The celestial spectacle known as the Northern Lights may grace the skies of Chicago starting Wednesday night into Thursday morning, captivating eager onlookers across the city.

Also known as aurora borealis, the lights may be visible on the low horizon in Chicago and seen overhead in Minneapolis and Milwaukee, according to the Geophysical Institute at the University of Alaska-Fairbanks. 

Those lights also could be visible in 16 other states besides Illinois, including Michigan, Indiana, New York, Vermont and New Hampshire. 

Billy Reed of Illinois Storm Chasers said clear weather is needed to see the Northern Lights, so the thunderstorms and rain forecast for Wednesday in Chicago could make it harder for people to catch a glimpse.

“At this stage when you’re two or three days out, it’s really hard to predict what cloud coverage is going to look like specifically after storms,” said Reed, a space weather geographic information systems specialist with the Storm Chasers. 

Weather and conditions permitting, the best viewing time in Chicago is 10 p.m. to 2 a.m., according to the Space Weather Prediction Center.

Michelle Nichols, director of public observing at Adler Planetarium, said auroras and the weather conditions needed to see them can be unpredictable and fast-changing, so there really is no perfect time. 

“Even though they’re being predicted for Wednesday night into Thursday morning, we truly don’t know when exactly to send people out,” Nichols said.

In Chicago, those who want to see the lights should avoid downtown. Light pollution can make seeing the lights more difficult, especially since the aurora borealis is dim to begin with, said Adam Miller, an astronomy professor at Northwestern University. 

“If one could find a relatively open field with sight lines to the north that’s in a dark location, and if you give your eyes the opportunity to adjust to the dark ambient light, that would improve chances to be able to see the aurora,” Miler said. 

Generally, the darker the area, the better the show, Nichols added, while Reed said to allow about 30 minutes for eyes to adjust to the darkness. 

Assuming the lights are visible Wednesday night, Miller said, onlookers should expect green or red hues.

Auroras occur when charged particles from the sun interact with Earth’s magnetic field. The particles become trapped in the magnetic field, then move toward the planet’s magnetic poles. When the charged particles interact with atoms high in Earth’s atmosphere, they cause atmospheric gases to glow, which creates the different colors people see in auroras. The types of atoms help determine which colors appear.

Miller said it’s rare to see the aurora borealis as far south as Chicago. In April, the Northern Lights were visible throughout parts of Illinois. 

Auroras tend to occur when there’s more solar activity, such as sunspots, and we’re approaching a period of greater activity, known as a solar maximum, Miller said.

“It’s not unusual that now and maybe over the next several months, there may be other events like this as well,” Miller said.

To Nichols, the beauty of the Northern Lights is watching what is essentially the sun touching Earth’s magnetic field.

“You are seeing interaction between the Sun and Earth,” Nichols said. “That in and of itself is amazing. We are not to completely separate objects in the universe. One interacts with the other and you’re seeing that.”