Displays of the northern lights—also called the aurora borealis—are possible on Monday evening in northern U.S. states as an incoming coronal mass ejection from the sun was detected arriving at Earth.

A CME is a cloud of magnetic fields and charged particles from the sun that streams into space at up to 1,900 miles (3,000 kilometers) per second. It can take a few days to reach Earth from the sun, but an exact arrival time is hard to predict in advance.

A “G2 Geomagnetic Storm Watch”—which the NOAA Space Weather Prediction Center called yesterday—remains in effect today, according to a post by the agency on X.

A geomagnetic storm is a disturbance of Earth’s magnetic field caused by the solar wind, but a G2 is not the strongest. The raging aurora seen across the world at lower latitudes on and around May 10 was caused by a G5 geomagnetic storm. The G2 geomagnetic storm predicted for tonight is “moderately intense” and means an auroral oval around the north pole that won’t reach as far south.

According to the SWPC, the U.S. states on or above the viewline—a prediction of the intensity and location of the aurora borealis—comprise Washington, northern Idaho, Montana, North Dakota, northern South Dakota, Minnesota, Wisconsin, northern Michigan and northern Vermont, northern New England and northern Maine. Much of Canada will likely see a display of aurora.

The viewline represents the southernmost locations where you may see the aurora on the northern horizon tonight. If you’re in one of these states and want to see aurora tonight, get away from light pollution and remember that the short hours of darkness will restrict the viewing window.

The solar wind in space causes the aurora—charged particles from the sun—being accelerated down the field lines of the Earth’s magnetic field. They occur in Earth’s ionosphere hundreds of miles above the surface.

The aurora was seen across the world on May 10 was the strongest geomagnetic storm for 21 years, with northern lights seen as far south as Arizona and Florida. Much of Europe and North America witnessed red and very rare blue-colored aurora.

The CME arriving at Earth tonight is from the same sunspot region—now called AR3697—that caused May 10’s geomagnetic storm.

May has been the most active month on the sun for decades, with 171 sunspots recorded. Sunspots are magnetic disturbances on the surface of the sun that can be as big as Earth and are where solar flares and CMEs come from. The sun is so active because it’s close to “solar maximum,” which the SWPC predicts will occur this year. The sun has a roughly 11-year solar cycle during which its activity waxes and wanes.

The northern lights are usually seen as an auroral oval around the North Pole at about 66-69 degrees north latitudes—the Arctic Circle. The best places to see them are Alaska, northern Canada, Iceland, Greenland, Norwegian Lapland, Swedish Lapland, Finnish Lapland and northern Russia.

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