So you know that thing where gloves are not as warm as mitten because of body heat?
It happens to your feet too. And that means that for a full time Vibram FiveFingers wearer in Iowa, it's a cold foot-season. So what do we do?
In the winter, I've figured out the few kinds of VFF's that are okay to wear casually if you're committed. First, the all-leather models are decent with a pair of mid-weight Injinji socks. This includes the Trek LS and the Speed LR's I talk about here. So far, the new Trek Ascent LR's are decent too, but may be a little colder due to the Hemp sections. (And it hasn't been that cold here yet.)
There are many new options for winter wear that look good. There are the Trek Ascent Insulated and the new Lontra LS that have recently been released. I don't have them so I can't say how they'll do. There are also the new CVT Wool's that are being delivered to my door tomorrow thanks to Vibram's Black Friday sales. I can't wait to try them out for wearing to the office this winter.
Other options for casual wear are few and far between. The other models I like to wear casually, like the CVT LS, CVT Hemps, or the original Speeds, are not warm at all when the weather is cold. If you spend any more time outside other than walking to your car, I'd stay away.
Though no longer for sale from Vibram, my 1 year old Lontras are my go-to shoes for cold weather. My wife and I each got a pair of them for winter running last year and we love them. Lontras are made with the Trek sole which is nice when you're running through snow and can't see the terrain underneath. Thinner soles may be a problem when you don't know if you're about to step on a big rock. They're also made with water resistant taped seams that keep your feet dry running through the snow and ice. They come up higher on your ankle and have extra insulation for keeping you warm. In fact, they're warm enough to wear with no socks and to have sweaty feet when you take them off.
The only downfall for me with the Lontras is the stiffness. Because of the insulation and the water resistance, they are much more stiff to wear. In fact, it took me awhile to like them because they would hurt my toes from wear. Thankfully, running in them a few times broke them in a bit and they're much more comfortable.
If you can get a hold of some original Lontras, I'd say go for it. If not, check out the new Lontra LS or the Trek Ascent Insulated for winter running.
Update - 12/7/15
Also, a good friend got a pair of the new Lontra LS this weekend and loves them. I love the new design even more than my original Lontras and he claims they're not too stiff. We'll see how they do running in snow without the high neoprene ankle cuff to keep them warm and dry, but they look great. I'd definitely consider them for casual and running use. and regarding warmth, his feet were sweating through church yesterday too.)