How do DC people dress for professional events? Help a too-casual Californian

Lived in DC briefly pre-Covid but haven’t been back much since, and I have a work event to go to — a convening/summit type thing. Not at the Capitol but politics-adjacent.

I don’t want to be the only guy in a suit and tie but I have no idea what most people wear to work events in DC now. Where I’m from anything more formal than a hoodie or fleece is practically black tie. Are traditional suits too fancy for most occasions now or am I just too Californian? Should I do some kind of sport coat and jeans situation?