It's been a long, long time since geomagnetic activity has been strong enough to bring the northern lights to the US in a significant way. However, less than two weeks after NASA announced the sun is moving away from solar minimum and officially began a new solar cycle (it started in December 2019), we're getting an opportunity to spot the aurora borealis from the US.
The Space Weather Prediction Center (SWPC) has announced G1 and G2 geomagnetic storm watches for nights from September 27 through September 29. Those watches are a measure of solar activity reaching Earth's atmosphere and alerts at that level indicate that the aurora may be seen in the northern US.
"Isolated G1 (Minor) geomagnetic storm conditions are likely to continue through [September 27-28]," the SWPC wrote in its notice. "A much larger coronal hole is expected on [September 29] further enhancing the solar wind conditions. A G2 (Moderate) storm watch has been issued for [September 29]."
Okay, that's a lot of information about a coronal hole. For a casual observer, the important part is that the northern lights are likely to be seen further south than you would see them under other conditions.
The map above, issued by the SWPC, reveals the potential southern reach of the aurora. It can be a little tricky to find your city on a map that small, but during the G1 alert periods, you're looking as far south as the green line. During the G2 alert, you're looking for the aurora to reach as far south as the yellow line. (See below for a breakdown of the timing.)
That area north of the yellow line includes northern Idaho, northern Iowa, Maine, Michigan, Minnesota, Montana, New Hampshire, New York, North Dakota, South Dakota, Vermont, Washington, and Wisconsin, in addition to all of Alaska and Canada. Though, the northern lights aren't exactly a rare occurrence in Alaska and northern Canada.
The video above can give you a sense of what the aurora borealis can look like over the US during a G1 watch. This was filmed by a stargazer in Graceville, Minnesota the night of September 26, 2020 during a G1 watch. Under these circumstances, you might not have the brilliant ribbons of bright light you'll find in, say, Iceland or Sweden, but the display is nonetheless moving.
Many variables have to align for the aurora to make an appearance. Nothing can guarantee the lights will show up on any given night, but the alert means the stars are aligning in your favor. At the time of publication (times updated September 28 at 5:30pm EST, times for September 27 have been removed), the SWPC's 3-Day Forecast projects a minimum of a G1 watch (Kp Index of 5) throughout the night of September 28 with a few periods of G2 watches (Kp Index of 6). Until 5am EST on September 29, there's at least a G1 watch. From 5-8pm on September 28 and then again from 11pm to 2am there's a G2 watch, which bring the potential viewing area down to the yellow line on the map above.
For the night of September 29, there's only a maximum Kp Index of 5 throughout the night, which is a G1 watch in the SWPC's watch system. (Southern reach of the aurora has the potential of getting to the green line.) That watch runs from 5pm on September 29 through 2am on September 30.
The northern lights are only visible when it's dark, so any of those earlier hours aren't much use to aurora hunters. However, if the forecast holds, there's a chance of seeing the display the nights of September 27, 28, and 29.
For the best view, you need to get away from light pollution, which is probably harder than most people realize. You really need a very dark sky. It's unlikely you'll see the aurora in a city, let alone a major urban hub like Detroit or Chicago. The further you are from city lights, the better your chances. This Light Pollution Map or the Dark Site Finder may help you locate an area with dark skies near you.
You'll also need the weather to cooperate. An SWPC representative previously told Thrillist, "You need very clear skies, a good view of the northern horizon (no trees, buildings, or hills), and it needs to be dark." The northern lights, seen this far south, will likely be visible along the northern horizon rather than directly overhead. You need both cooperative weather and an unobstructed view to the north.
The key to crossing the incredible display off of your bucket list is persistence and patience. Once you're in your spot of choice, you're going to need to be patient and keep your eyes on the sky. Just because it's not there one moment doesn't mean that it won't be soon. Likewise, if you see it, that doesn't mean it's going to be around all night. It's a bit like whale watching in that way.
The northern lights are visible in the northern US from time to time, but it's easy to take it for granted. It's been a long time since US residents have had a chance like this. Get out there and enjoy the incredible sight if you're lucky enough to find it.