I got a pair of Salomon TOUNDRA mid WP boots and have been using them for the past couple days with my fatbike. We've had windchills here in SE Wisconsin as low as -45F. My feet have been warm throughout the ride. The boot is incredibly light too. So if you're looking for a lightweight boot to run with your flats/platforms, these have the insulating properties of a Sorel pack boot, but not much heavier than a running shoe.