#9d00m

As @9d00m said, he has both temporary and permanent lichtenberg figures on his skin, and when he uses his powers, the energy visibly arcs down the figures and into his hands or to wherever he's channelling the power.

When he's on a beach, if his powers are even slightly active, or just under the surface, Jay's footsteps on the sand creates small areas of fulgurite crystals in his path.

Whenever there's a lightning storm outside, or even somewhere close by, Jay's eyes flicker a bright blue just before the lightning actually strikes.

He knows exactly how far a lightning strike is away from their current position, no need to count the seconds between seeing the bolt and the clap of thunder that follows.

Contrary to popular belief, his hair is very tame for someone who's always charged with static electricity. His hair just doesn't seem to stand on ends, but other people's hair in his presence, that's fair game.

Some of his freckles are joined up by lichtenberg figures, no one knows why or how, but lightning seems to move between them like an elemental dot to dot.

Sort of a funny thing, but clapping, as in hand clapping applause. Jay's clapping can easily drown out a small room.

Which also means, if he puts his power into it, he could generate a thunder clap capable of deafening people if he tried.

Jay is really, really good with flowers or potted plants. His lightning helps them grow, due to its extreme heat, it bonds oxygen and nitrogen in the soil and the plants just thrive.

He's used his powers to try and cook food, don't tell me otherwise. It didn't end well, but he tried it.

When it comes to building stuff, such as the monestary every time it's destroyed, lightning can strip the bark off trees, all Jay has to do it touch them.

Jay's powers have so many more possibilities than just the lightning guy. He's been shown to teleport when he achieved his true potential! Lightning is so much more than arcs in the sky.