The northern lights are a frustratingly elusive but spectacular sight for those who witness the eerie glow in the sky.

"It was otherworldly," said Kathy Wedl of Edina, who saw the green lights as she and her husband drove home from Up North. "We tried to chase it, but we weren't successful."

That was 40 years ago. "I had never seen it before — nor since," she said. "And I'm just wondering if I was dreaming."

That prompted her to ask where and when people have the best chance to see the northern lights in the state, submitting the question to Curious Minnesota, the Star Tribune's series fueled by questions from readers.

She's not the only one intrigued by the aurora borealis, which has become a growing worldwide attraction, with tourists flocking to far-flung spots for aurora-hunting tours and cruises. But with luck and patience, Minnesotans might see it right here this month.

"The most important thing is patience," said Bob "Astro Bob" King of Duluth, an amateur astronomer and retired Duluth News Tribune photo editor who's seen the aurora some 400 times in Minnesota over 40 years. "I understand the draw because it's such a beautiful phenomenon."

First, the aurora is unpredictable. Even if the lights are anticipated, they might never materialize, which is what happened last winter. Although the lights can be viewable any time of the year, King said spring and fall, especially September and March, are the best chances here. An aurora sighting is possible in Minnesota late Saturday night and Sunday and again Sept. 27-30.

The recipe for seeing the spontaneous solar show: a dark night sky without a bright moon, heavy cloud cover, light pollution or trees filling the horizon. There also needs to be a high Kp — the measure of geomagnetic activity from zero to nine. The National Oceanic and Atmospheric Administration's Space Weather Prediction Center tracks the Kp, and apps help aurora chasers monitor the Kp.

The farther north, closer to the magnetic pole, the better the chance you'll see the lights, often after midnight. When the Kp hits 6, the aurora can be visible as far south as the Twin Cities.

What is the aurora? Solar flares and coronal holes on the sun spray streams of high-speed particles into space. If they connect with the Earth's magnetic field, they are guided into the atmosphere where they slam into oxygen and nitrogen atoms, exciting them to give off light, King said.

Cameras capture fainter colors that human eyes can't detect, leading to photos of vibrant green, purple and red auroras that may look gray or pale green in person. (Go to strib.mn/aurora to learn how to capture the aurora.)

Minnesota is tapping more into the northern lights' popularity. A national summit started two years ago in Two Harbors and will be held this fall in Wisconsin. Minnesota's tourism office advertises the northern lights to visitors, and Cook County touts its dark skies on Lake Superior. In the metro, the aurora has inspired lights at Allianz Field and Minnesota's 2018 Super Bowl gear.