Northern lights over Maine in 2015.  (Mike Taylor)

The aurora borealis may light up the skies tonight as far south as the Midwest. A G3-strong geomagnetic storm is shaking the earth’s magnetic field as a high-speed solar wind stream sweeps by. This fast solar wind emanates from a large coronal hole, a void in the sun’s corona allowing the uninhibited solar flow to escape.

About a month ago, this same coronal hole caused G2-moderate storm conditions, and lit up a brilliant aurora in the process. This time it’s slightly stronger. Stable coronal hole structures affect the earth on about a 27-day period, so we could be having this same conversation again on November 21.

Expect the disturbance to linger through October 26. With a new moon on October 30, the dark sky is favorable for aurora viewing, especially at high latitudes.

Baseball fans will be up anyway; if the skies are clear you might get lucky. The Cubs haven’t repeated in 108 years, the Indians in 68. Recurrent anything would be a joy to either team.

Even if you’re farther south than the aurora typically stretches, this might be the night you can cross it off your bucket list. Pennsylvania, Ohio, Indiana and Illinois have a shot at seeing this one, plus all the states to their north, if the clouds cooperate. In the Plains, it could reach down to Nebraska. Those of you in the state of Washington could catch a glimpse, too.

Keep an eye on the planetary K index tonight. If it’s at 7, then the areas we mentioned above may be able to capture it with a long-exposure photo. If the K-index spikes higher than 7, it’s possible that areas in the Midwest could see it with the naked eye, and people in the D.C. region could catch it in a photo.

Thirteen years ago, the Halloween Storms were probably the most disruptive few weeks of space weather since the space age began with Sputnik 1957. The sun caused extreme (category 5) geomagnetic storms and radio blackouts, and severe (category 4) solar radiation storms. Satellites were disabled, power grids blacked out, and aircraft re-routed during the most intense periods of the fusillade of solar eruptions.