A 'severe' geomagnetic storm is forecast for Earth for the first time in years — here's what to know about these storms

• NOAA issued a G4 geomagnetic storm watch for the first time in nearly 20 years.
• This type of storm generates dazzling aurora, but can also cause radio blackouts and outages.
• Experts say we should look out for aurora borealis, but shouldn't worry about major issues. 

For the first time in nearly 20 years, the National Oceanic and Atmospheric Administration has forecasted a "severe" G4 geomagnetic storm to hit this Friday, dazzling states across the northern US with aurora borealis.

G4 storms are the second-strongest type of geomagnetic storm. "If geomagnetic storms were hurricanes, 'severe' would be category 4," according to SpaceWeather.com.