A small travel dilemma for you all:

So I'm going to Greece next week for a conference. I've been twice before and I know very well what to wear (casual) and what the weather will be like (hot, definitely don't need a real coat, just a light topper for AC and evenings is plenty.) However, I have a 9 hour layover in Zurich on the way back, so I thought I'd pop into town (it's a 15 minute ride on the train), eat some chocolate and cheese, see a couple of sights, and go back to the airport. So do I need to bring a coat for this part of my trip? If I did it would most likely be my black trench coat. Or could I get away with something like a mid-weight blazer (or maybe my plaid riding jacket) worn as outerwear? I would prefer to do the latter just because those things could also be worn as toppers for AC during the conference, and are smaller/easier to pack than my trench. Plus it just annoys me to have to spend suitcase space on something that will only get worn for a few hours. I'd rather have that space for more shoes, lol. I will also have a big wrap of some sort for the plane that I could wear for additional warmth.

I will only be in zurich during daylight hours if that matters. And I run warm, but not super warm.