I get some weird looks around town and sometimes at work, but for the past few years I've been wearing Birkenstock closed-toe sandals year-round. In winter I wear thick wool socks (Smartwool, REI, etc) and I ride in any weather. Firstly, the thick suede upper is pretty water resistant, so the fronts of my feet don't get wet. Secondly, if my heels get wet because they're exposed, I don't feel it because the wool wicks it away. Usually after just walking around for a few minutes it all dries up because there's always air circulation. I rarely have to change out my socks, although I keep a few pairs of spares at work just in case.