A gleaming display of northern lights illuminated the sky above Point Reyes this weekend, courtesy of an intense geomagnetic storm—one of the most powerful since 2003. Residents captured photos revealing a horizon pigmented with magenta and green hues, although many had to wait until late into the night to do so. Kathy Runnion, who lives in Inverness Park, said she prepared by allowing her eyes to adjust to the darkness for hours. Then, at around 11 p.m. on Friday night, she began to see a red glow envelop the sky from her backyard. “I knew that you might not be able to see it with your naked eye, but your cell phone’s camera could pick it up,” she said. “It took me a little bit to get the settings right, but then I really started to see it.” Also known as aurora borealis, northern lights occur when ejected material from clusters of sunspots—temporary patches of cooler, darker areas on the solar surface—collides with the Earth’s atmosphere. “During periods of heightened geomagnetic storm activity, the aurora becomes more widespread and visible at lower latitudes,” the National Oceanic and Atmospheric Administration said. On Friday, NOAA’s Space Weather Prediction Center, which measures geomagnetic storms on a scale of one to five, announced that conditions were likely to reach level four or higher. The storm’s intensity slightly diminished on Saturday evening before resurging on Sunday. Fiona O’Kelly, a ranger for the Point Reyes National Seashore, said the park was busy fielding calls about the best spots to watch the light show over the weekend. “I think the first night kind of snuck up on people, so nobody was really expecting it to be like it was,” she said. “But then once everybody saw the pictures, they came out. We got a lot of phone calls.” Low-lying coastal fog obscured visibility on Saturday, so Ms. O’Kelly directed most people inland, where they had a better chance of seeing the aurora from surrounding high points. Nonetheless, many still ventured out into the park in search of the lights. “Everywhere along the road, cars were pulled over trying to find them,” she said.