The northern lights may be visible further south than usual tonight. Here's where and how to watch.

WASHINGTON — Skywatchers in 18 states may be treated to a colorful light show Tuesday evening as the northern lights could appear across North America, according to forecasts.

The aurora borealis phenomenon began late Monday, and is expected to last through Tuesday night.

The ethereal lights that make up the celestial show may be visible further south than is typical , according to the US National Oceanic and Atmospheric Administration’s Space Weather Prediction Center.

What causes Aurora Borealis?

The light show is caused by "a long-duration M2.7 flare that peaked at approximately 30/2002 UTC," according to the agency. "An associated full-halo coronal mass ejection (CME) was observed in coronagraph imagery."

In layman's terms: the sun is constantly shooting out charged particles.