A geomagnetic storm is expected to erupt on Earth this week, possibly triggering an appearance of the northern lights, also known as the aurora borealis, according to the National Oceanic and Atmospheric Administration's Space Weather Prediction Center.
But will the lights be visible in Illinois? And when should you head outside to take a look?
Here's what we know.
What are the northern lights?
The auroras are a natural light display in Earth's sky that are famously best seen in high-latitude regions of the Northern and Southern hemispheres.
The phenomenon is caused when electrically charged particles from space enter Earth's atmosphere and collide with molecules and gases like oxygen and nitrogen, causing the atmospheric particles to gain energy. To return to their normal state, the particles release that energy in the form of light, according to the University of Alaska at Fairbanks Geophysical Institute website, which tracks the phenomenon.
As auroras form, Earth's magnetic field redirects the particles toward the poles through a process that produces a stunning display of rays, spirals and flickers that have fascinated humans for millennia. Whether hues of green, red, blue and even pink dance about in the sky depends on the altitude where the collisions occur, as well as the composition and density of the atmosphere at the time.
When will northern lights be visible?
Even though conditions are prime for more impending aurora shows, experts have long struggled to accurately forecast exactly when and where the phenomenon will ever occur. Even the best predictions can accurately be made only a few days or even hours in advance.
But the aurora is forecast to appear on Thursday, Aug. 7.
As a rule of thumb, if the weather is clear, the best aurora is usually visible within an hour or two of midnight, according to NOAA. And if it looks as if the northern lights will flare up near you, you should get away from cities and travel to dark locations free from light pollution so you can best see them.
The agency also maintains an aurora dashboard that should help skygazers track the phenomenon. NOAA's 30-minute aurora forecast may be particularly useful for regular updates on viewing opportunities.
Where could auroras be visible?
For most of the time, auroras are best seen around the magnetic poles of the Northern and Southern hemispheres in Europe, Asia and North America. In the U.S., Alaska is well known to have the best viewing opportunities for the northern lights.
But a geomagnetic storm tracked by the NOAA is expected to make the auroras visible farther from the poles.
The geomagnetic activity detected by NOAA's Space Weather Prediction Center has a Kp index of 6 on Thursday, Aug. 7, meaning the northern lights will be active and brighter further from the poles, according to the agency.
"At this geomagnetic activity level, it might be possible to see the aurora from the northern edge of the United States," NOAA says on its website.
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Will northern lights be visible in Illinois?
Illinois is one of the southernmost locations where you may be able to see the aurora on the northern horizon.
Aurora borealis may appear again on Friday
The geomagentic storm will be less powerful Friday, Aug. 8, but is forecast to still be strong enough to trigger the northern lights once again across the northern U.S.
By then, though, NOAA predicts the KP index will be downgraded to a 5, which still means the auroras are still bright further than usual from the poles.
"If you are in the right place, these aurora can be quite pleasing to look at," according to NOAA's description of of 5-rating on the KP scale.
Will skies be clear in Illinois during northern lights?
Central Illinois will see scattered showers and thunderstorms on Thursday evening, mainly before 8 p.m., before skies turn cloudy, with a low around 72 degrees, according to the National Weather Service. Skies are forecast to be mostly clear on Friday night with a low around 73 degrees.
Chicago will be similar, with a 50 percent chance of showers and thunderstorms on Thursday evening, mainly after 8pm, and a low around 73 degrees with clouds. Friday night will be mostly clear in the city, with a low around 76.
This article originally appeared on Journal Star: Will aurora borealis be visible in Illinois? Here's when, where to look
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