Even if it's mounted to a wooden 4x4? If so, put an actual lightning rod kinda near it and ground that really good. Lightning should go for that instead.
We've grounded everything at my house six ways from Sunday; we've had multiple professionals look into it. Nothing helps. They keep telling us it's the underground river, but maybe we're on a junction of two magnetic ley lines or something (hell, as good an explanation as any at this point