I agree with pretty much all of the previous posters.
I will second the idea of having something to wear that is water
proofresistant. There was some form of precipitation nearly every day, and if you're waiting out a passing shower instead of getting out there, you'll never get anything done, and an umbrella is not only cumbersome, but blocks your view.
I wore boot cut jeans with fairly fitted waist, brown dr martens boots, and layered sweaters with a thick cotton coat (from Old Navy) for pretty much all of my time there. The coat wasn't actually water proof, but the rain never made it all the way through to my skin (it doesn't seem to rain HARD there very much) I never felt out of place. I would worry less about the sweaters, most people will be seeing you in the outer wear.
I had one knee length knit dress, flats, wide belt and panty hose (I never saw people go bare-legged, not sure if it's a temperature thing or not) for the wedding we were attending, and also for nicer dinners.