Before there was a "super" flare and/or CME you'd see the sunspot with your unaided eyes. Check out "The standard flare model in three dimensions. II. Upper limit on solar flare energy" and the figure 4 in particular for size to energy reference. https://arxiv.org/abs/1212.2086
AIUI, it's only a problem if sufficiently long wires are actually connected to vulnerable equipment.
"Although X is the last letter, there are flares more than 10 times the power of an X1, so X-class flares can go higher than 9. The most powerful flare on record was in 2003, during the last solar maximum. It was so powerful that it overloaded the sensors measuring it. They cut-out at X17, and the flare was later estimated to be about X45. A powerful X-class flare like that can create long lasting radiation storms, which can harm satellites and even give airline passengers, flying near the poles, small radiation doses. X flares also have the potential to create global transmission problems and world-wide blackouts." (1)
The question is when.
https://thecomicninja.files.wordpress.com/2013/04/calvin-and...
Worth googling, good short story, and relevant to the "Solar superflares hit Earth" topic.