A U.S. government agency that monitors solar activity warned on Saturday (May 11) that the biggest geomagnetic storm to hit the Earth in two decades would continue through Sunday – posing risks to radio, GPS and satellite communications and bringing the aurora borealis to areas unaccustomed to the celestial light show.

The National Oceanic and Atmospheric Administration (NOAA) described the event as “extreme” and said the last event of a similar scale occurred in October 2003, when electrical installations in Sweden and South Africa were damaged.

NOAA said geomagnetic storms were likely over the weekend as several coronal mass ejections headed towards earth.

NOAA said the cause was a large complex sunspot cluster that was 17 times the diameter of the earth.

(Reuters)