I say that without any documented proof (it was destroyed in the fire) and inspite of the fact that the re-attachment surgeries and impaired circulation surely compromised blood flow to his feet. I believe those giant boots and three-inch-thick soles would have kept his two left feet warm in the mountains.
Lake's 303 MXZ winter boots have a touch of the monster about them, and the aesthetic is exaggerated by the desirability of sizing them to allow for heavier weight socks while leaving heat-trapping air space around your toes. My original choice to go up one size to 44s didn't provide enough room so I sent them back to bikenashbar.com for a pair of 45s. Online advice regarding sizing gets complicated because the boots are available in normal and wide widths but I'd say the consensus is one to two sizes larger than your summer shoe or one size larger in the wider width might describe the sweet spot for thermal happiness. In practice the added bulk is tempered by the soft padded interior and comfortable fit. My size 45 303s weigh 739 g each, twice the weight of my summer shoes but in practice they don't feel that heavy.
The thick Vibram rubber sole is easy to walk in and my un-shimmed SPD cleats sufficiently recessed to avoid contact with the pavement entirely. When clipping in the generous sole "mutes" the connection just a little but by my second ride I was finding the pedals perfectly. The up-sized 303s add fractionally more toe overlap with my Enigma but it's nothing consequential.
I don't know about you but what I hate most about riding in winter, or what passes for winter in Northern California, is the extra time it takes to layer up. Above all winter riding requires preparation and organization. Everything in the garage close at hand so that TTRO (time to roll out) is never more than 10 minutes. That means a charged battery for my tail light, helmet, glasses, spare tube, filled water bottle and tires pumped before hitting the Strava start button on my iPhone, punching in the door code and rolling away. Make TTRO longer than 15 minutes and my motivation suffers.
The 303s reduce my TTRO and completely eliminate the hassle of overshoes. Overshoes get snagged and torn; zippers eventually fail. They feel best when they fit like a second skin over your shoes, but I'd much rather just put on a pair of shoes appropriate for the conditions and be done with it. So how warm are they? I've worn the Lakes several times in the 40s and one early morning into the thirties and my feet stayed warm in two layers of summer socks for two hours. Frankly I've lost my Canadian anti-freeze plasma and I'm not interested in riding when it's colder than that but I'm sure with a heavy sock the 3M Thinsulate-lined toe box and Thermosol insole would be good down to the freezing point. Beyond that much would depend on individual thermodynamics. Similarly I can't comment on how water repellent the 303s are but all cycling shoes/boots will suffer in a downpour by wicking action from socks or water intrusion through the cleat cutout in the sole. If you want to arrive at work or back home with dry feet in a downpour then you need to wear rain pants.
The exterior of the 303 is water-resistant Pittards® WR100 full-grain leather available with either yellow or silver graphics. I chose the silver. The BOA closure system provides optimal pressure and integrates well with the tongue liner making for a very plush fit without being sloppy. All things considered the Lake 303 MXZ is all the winter shoe I'll ever need and then some. If you live in a climate with a real winter they are definitely worth a look just be prepared to scare a few villagers. You can purchase them as I did from bikenashbar.com. Next Review Giro Ambient winter gloves.