That's a matter of opinion. I don't do cold well, and anything under 74 is cold to me. And, if I'm wet, I'm going to be colder than whatever the actual temperature is.
Anyway, to answer the question: We take rain pants (I find they are a great 2d layer on my legs), rain jacket (with hood) and waterproof shoes. That's usually sufficient over layers when it's rainy.
I wouldn't bring an umbrella. Couple of reasons - in a crowd it can be a weapon (those metal points on the end of the ribs can poke an eye), and you'll really want to have two hands free when out and about.