The northern lights once again lit up the Bay Area night sky Tuesday and are expected to be visible again late Wednesday across much of the northern United States, reaching as far south as Northern California.

The dazzling display was triggered by a geomagnetic storm that allowed the Aurora Borealis to be seen much farther south than usual.

Why the northern lights are appearing more often

The sun has reached the peak of its 11-year solar cycle, a period of heightened activity that produces stronger solar flares and magnetic disturbances. This has made aurora sightings more frequent and widespread, with vivid colors painting skies in places that rarely experience the phenomenon.

Auroras — known as the northern and southern lights — occur when charged solar particles collide with gases in Earth’s atmosphere, producing glowing streaks of color typically visible near the poles.

However, as the sun’s magnetic poles reverse, a process that happens roughly every 11 years, the resulting magnetic turbulence allows solar energy to reach farther across the planet.

Last year, Earth was hit by the most powerful geomagnetic storm in 20 years, creating spectacular aurora displays across the Northern Hemisphere. Soon after, another major solar storm illuminated skies in places as far south as Germany, the U.K., New England, and New York City.

According to NASA and NOAA, this surge in solar activity will likely continue through the end of the year, though scientists won’t know the exact peak of the solar cycle until several months later.