There are five categories of solar flares: A, B, C, M and X. They are measured by their X-ray brightness. Type A and B are negligible and type C have very few effects on the Earth. Type M are medium and can cause brief polar radio blackouts. X-class flares are the big ones and can cause planet wide radio blackouts and long lasting radiation storms.

Each class of flare is subdivided into a nine point scale i.e. M 1 to M9 an X1 to X9. Although some flares have been estimated to have been X45! The direction of the flare with respect to Earth is key. A X9 or bigger flare pointed directly at the Earth would not be good for the electrical grid to say the least.

You can check the Suns current conditions at: http://www.spaceweather.com/

The above example has only a 5% chance of an X-class flare which is both fairly low and fairly common. It is a great site to monitor. Thanks mamaizzy.

Spaceweather.com is one place I check daily. Today an M 5.6 was released from the sun. I get texts on my phone about it too... I signed up for satellite flybys and get updates on everything from nasa now lol
I also have QuakeFeed, Weather Underground (worldwide) and google earth, leafsnap, a dozen other survival apps... I understand in some emergencies these won't work but in the majority, they most likely will. 🙂 and they were all free so, win win lol

X-class flare expected within the next 3 days, but the Solar magnetic field is still northern. (north=good/south=Bad)