Parts of California could see the northern lights this week due to a severe geomagnetic storm predicted by the NOAA Space Weather Prediction Center. Space weather forecasters at the center have issued a Geomagnetic Storm Watch for Thursday into Friday. How strong was May’s solar storm that caused low-latitude northern lights? The watch is rated G4, just one level shy of the maximum, and it was issued after a strong ejection of solar material on the sun's surface on the evening of October 8. According to NOAA, the material is traveling toward Earth and is expected to arrive as early as the morning to midday Thursday and continue for some time until all of the material passes. Northern lights vs. southern lights, what’s the difference? When the material is around 1 million miles from Earth, a more detailed time and intensity can be measured by satellites, NOAA said. When a coronal mass ejection happens, a lot of solar material is blasted into space, and if this hits the Earth, it interacts with the magnetic field, primarily at the north and south poles. This is what creates the northern lights, also known as aurora borealis. Depending on how strong the ejection is can mean that places in lower latitudes can observe the lights. Earlier in 2024, strong ejections sent the lights to places close to the equator. While the auroras can be stunning to see, the solar material can also affect power grids, satellite communications and other technology.