New home - dimmers adjusting to 53% during storm?

Where this came from: this question was asked on r/Lutron — not here. We answered it there, in public, and this is that answer.

The timing points at a power event, but not in the way people usually assume. Lutron documents power-failure memory on its Caseta dimmers: after an interruption they return to the level they were at (https://assets.lutron.com/a/documents/369804b_Caseta%20In-Wall%20Dimmer%20Spec.pdf), so jumping to a new level isn't the documented behaviour of the dimmer on its own. That's why the model numbers and the rest of the system matter here. The oddly specific 53% is worth noting: nobody slides to 53, so something sent that level or reported it. The third dimmer not moving would make sense if it's on a different circuit and didn't see the same event.

Before anyone sells you anything, I need to know what you actually have, because the answer is completely different depending on the platform. Pull the faceplate off one of the two that moved and read the model number printed on the metal frame. Also tell me whether there's a Caseta Smart Bridge, an RA2 Select main repeater, or a wall-mounted processor in a closet somewhere. If it's standalone Maestro or Diva with no hub, this is dimmer behavior and there is no setting to chase. If there's a processor involved, the level could have come from the processor instead, and that's a different conversation.

The thing I'd check while you're at it is surge protection at the panel. Since the 2020 NEC (230.67), a home's service is supposed to have a surge-protective device where the state has adopted that code, so look in the panel for a breaker-mounted or panel-mounted one. If there isn't one, an electrician can add it, and it protects every dimmer in the house, not just the two that misbehaved. Two dimmers jumping to an odd level is harmless. The same events cooking the electronics over five years is not.

What I would not do yet is replace anything. Twice in one storm is consistent with the power, not with a bad dimmer. If it keeps happening on clear days with no flicker, that's a different problem and worth chasing.

If you post the model numbers off those two dimmers and whether you have a bridge or a processor, that narrows down whether the level came from the dimmer, the bridge, or something integrated with it. (I'm a Lutron dealer; there's nothing to sell you on this one.)