I ride in extreme temps as does everyone that winter bikes in Alaska. All these suggestions are good. I personally prefer hand warmers to toe warmers. Winter boots for riding should be comfy (large) enough to fit small hand warmers. I've never found the toe warmers to be effective at all. I also agree that Keen boots are typically light. At -20F, winter boots are pretty much the requirement. You can choose very well insulated boots and wear them without any chemical packs inside or vapor barrier or anything, or you can get lighter boots and toss in chem packs. By the time you are using a winter boot it should be windproof. Vapor barrier socks or simple plastic baggies really do make a difference. So does applying Mitchums (sp?) anti perspirant on your feet the night before. It probably isn't quite as effective as a vapor barrier but it's a useful thing to do. When you look at boots be careful to check exactly what type of insulation is used. I do like Keen as they seem to make decent boots that are light and have a good weight to warmth ratio. There are also over boots like Neos (if I recall that name correctly) that are very effective. Keep in mind it is critical that your boots be large enough to fit with an appropriate set of socks inside and still be roomy enough that you don't have to have them on tightly. Any boot that is snugged down tight can reduce blood flow and that will bring on cold feet fast. I follow my own advice. As temps here begin to fall the first thing I do on my road bike is to grab my larger road shoes and wear thick socks with a plastic bag (cheap grocery store bag) that I cut the end off (put over my socks). I also have warm overboots for my road shoes but they don't come close to taking me to -20. By that time I have my Keen boots on and I toss in a hand chem warmer in my boot. They take nearly 10 min to get up to temp and for me they last for at least an hour or two. Sometimes I'll just wait till my feet are feeling chilly and pull out a chem warmer and open it, then in ten min I'll stop and put them on. Whatever works, eh?