According to Spaceweather.com, sunspot group 1302 poses a major risk for X-class solar flares and it is still growing, and will face Earth this next week. This is the largest solar cycle 24 sunspot cluster so far and is producing M and X class solar flares. In a couple of days this large unstable sunspot will be facing the earth.
It was sunspots flares emitting X class flares that that have impacted electronics systems on the earth. In March 1989 a major flare caused the Hydro-Quebec power grid in Canada to go down for over nine hours. The resulting damage and loss in revenue were estimated to be in the hundreds of millions of dollars. A 1994 solar storm caused major malfunctions to two communications satellites, disrupting newspaper, network television and nationwide radio service throughout Canada.
The grand daddy of all flares occurred in 1859, before we had a power grid. This super storm was discovered by Richard Carrington and became known as a Carrington Event. This September 1859 event created havoc for the recently established telegraph systems, shocking operators and causing fires in the telegraph offices. Think about the havoc it could have caused our current wobbly power grid. Stay Tuned.
Update (09-25-11, 8:45) Anthony Watts has an excellant post on this up coming X-class flare HERE.