A severe geomagnetic storm is forecast to hit Earth’s magnetic field on Wednesday, which could cause widespread disruption to infrastructure technology and make northern lights visible for much of the northern half of the U.S.
The National Oceanic and Atmospheric Administration on Tuesday issued a G4, or severe, geomagnetic storm watch in response to recent coronal mass ejections, or CMEs, from the sun. The highest geomagnetic storm level is G5, which is considered extreme.
The latest CME was the “most energetic and fastest of the CMEs” that erupted in the past few days, NOAA said. It was also associated with one of the strongest solar flares of the current solar cycle. The flare peaked around 5 a.m. ET Tuesday and was classified as an R3 or “strong” flare, meaning it has the potential to cause major disruptions to high-frequency radio on the sunlit side of Earth and cause low-frequency navigation signal issues.
The severe storm is expected to impact Earth around mid-day Wednesday, the Space Weather Prediction Center said, although it noted the forecast is “tough” and it only had a “moderate level of certainty” on the timing.
Another G3, or strong, geomagnetic storm was expected to affect Earth on Thursday, NOAA said.
NOAA/Space Weather Prediction Center
While the potential geomagnetic storms can cause disruptions to critical communication infrastructure, they could also make the aurora visible as far south as Alabama and Northern California beginning Tuesday night, NOAA said.
The University of Alaska and Space Weather Prediction Center forecasts say the best chance of seeing the northern lights starts as early as 10 p.m. ET Tuesday and will last until around 1 a.m. Wednesday.
During that time, “highly active auroral displays” might be visible in places like Portland, Oregon; Cheyenne, Wyoming; and New York City, the University of Alaska said. The northern lights might also be visible close to the horizon as far south as Oklahoma City and Raleigh, North Carolina, the university said.
NOAA/Space Weather Prediction Center 
In May 2024, a powerful coronal mass ejection brought the strongest geomagnetic storm in over 20 years to Earth. During the CME, multiple X-class solar flares were recorded. That storm caused some radio blackouts.
Another strong geomagnetic storm in October 2024 led to the northern lights being visible as far south as Florida and over bright areas like New York City and Chicago.
