People in more than 15 states in the U.S. may be able to see the Northern Lights on Monday night.
Following a massive eruption of plasma from the sun—known as a coronal mass ejection (CME)—over the weekend, the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center has issued geomagnetic storm watches for Monday and Tuesday, which could lead to colorful auroras.
Read more: See the 9 Most Breathtaking Photos of the Northern Lights
Here’s where they may be visible—and how you could best see them.
What causes the Northern Lights?
NOAA issued its geomagnetic storm watches after the detection of a CME erupting from the sun on Saturday. A CME occurs when the sun releases an explosive burst of plasma and magnetic fields into space. Those ejections can then hit Earth hours or days later.
When a CME reaches Earth, the charged particles can react with molecules in the planet’s magnetosphere—the region around the Earth where its magnetic field lies—to produce a geomagnetic storm. Such storms in turn can create auroras, vibrant displays of light that can appear in a variety of colors depending on the gases struck by the solar particles and how high up in the atmosphere the collision occurs.
NOAA rates the severity of geomagnetic storms on a five-point scale, with G1 storms being considered “minor” and G5 storms “extreme.” Stronger geomagnetic storms increase the likelihood of auroras being visible closer to the equator.
The CME that exploded from the sun on Saturday is expected to reach Earth’s atmosphere on Monday. NOAA has forecast that it could produce a strong, G3-level storm on Monday and a moderate, G2-level storm on Tuesday.
When and where could they be visible on Monday?
The intensity of the auroras will primarily depend on timing.
During the day, any such light displays are blocked out by the sun and not visible. The geomagnetic storm resulting from the CME was forecast to be strongest on Monday between 11 a.m. and 2 p.m. ET, according to NOAA, with a G3 storm possible during that time.
Luckily, however, NOAA forecast that geomagnetic activity could remain high into Monday evening, with a G2-level storm possible up until 8 p.m. ET and the strength then gradually decreasing into the night.
That means auroras could be visible on Monday in the northern U.S. and Canada and—if the intensity of the storm does reach the stronger G3-level and stay there—could be visible further south still.
According to NOAA’s geomagnetic storm scale, G2-level storms could lead to auroras being visible as far south as New York and Idaho. At G3 levels, they could be visible even farther south, in Illinois and Oregon.
Notably, the forecast arrival times of CMEs can change by hours, which could lead to brighter-than-expected auroras in the sky Monday night. So for the most up-to-date information, keep track of the forecast as nightfall approaches in your area.
How can you see them best?
The lights are best seen at night and in clear conditions, away from cities and light pollution and without cloud coverage.
Cameras capture the lights better than the human eye, so viewing them through a lens may make the colors appear brighter. If you’re taking a photo, remember to use a long exposure for the best results.
The post The Northern Lights May Be Visible in Much of the U.S. Monday Night. Here’s Where and How You Could See Them appeared first on TIME.
