How much damage are we talking about here. Capable of destroying a city? County? State? etc.

Depends how far he can extend his 'heat' but under normal and consistent showings, ramped up to how much is usually suggested, he could unleash if he was desperate enough and had a need to, I think a city would be a good general level to suggest. He destroyed a school once right? I mean, something like that, but no students were there I think. This is based on my reading of him, which is limited somewhat.