This alert comes as two coronal mass ejections (CMEs) are expected to make their way to Earth this weekend. A geomagnetic storm occurs when solar wind — a stream of charged particles from the Sun — collides with Earth’s magnetic field.

For prime northern lights viewing in the United States, the strongest activity is expected to arrive late Saturday into Sunday, per Thursday’s forecast by the National Oceanic and Atmospheric Administration (NOAA). Clouds may also clear through the night to provide good vantages for the majority of the country.