I swear by the Pearl Izumi WxB P.R.O. Barrier shoe covers. I commute 10 km each way all year round on the west coast of Vancouver Island, in Canada. It rains on average about 2 meters a year here, and most of that is Nov to Feb. As I write this it's 6 am and it's rained 25 mm since midnight. I'm on my third set of these since 2012, and they've never let me down, but they do wear out eventually. The bright yellow ones are highly visible, but they only lasted 1 1/2 seasons. I wear them over light weight leather road shoes (spd) and even down to -11C they're fine for a 25 minute ride.