The northern lights may be visible across 18 states in the U.S. tonight due to a geomagnetic storm. This event is linked to a coronal mass ejection (CME) from the sun that occurred over the weekend. The National Oceanic and Atmospheric Administration's Space Weather Prediction Center has issued a storm watch, indicating that auroras could light up the night sky.

The CME is expected to impact Earth between Monday night and Tuesday morning. Forecasts suggest geomagnetic storms could reach levels between G2 and G3 on the scale used to measure geomagnetic activity. The KP Index, which ranges from 0 to 9, is predicted to hit a level of 6 tonight.

States where the northern lights are most likely to be seen include Alaska, Montana, North Dakota, Minnesota, Wisconsin, Michigan, Maine, South Dakota, Vermont, New Hampshire, Idaho, Washington, Oregon, New York, Wyoming, Iowa, Nebraska, and Illinois. Visibility will depend on local weather conditions, particularly cloud cover.

The auroras, also known as the northern and southern lights, are caused by charged particles released during solar explosions. When these particles collide with atoms in the Earth's atmosphere, they create colorful displays in the night sky. The best time to view the lights will be just after sunset or just before sunrise.

Even if the auroras are not directly overhead, they can be seen from up to 1,000 kilometers away under the right conditions. For those unable to see the lights with the naked eye, digital cameras may still capture the phenomenon.

While the geomagnetic storm is expected to continue into Tuesday, conditions are likely to return to quieter levels by Wednesday as the effects of the CME diminish.