I'm going to keep recommending Benbo until people start listening. The knobs and levers are huge and easy to use with heavy gloves/mittens, the legs are "upside down" (with the fat tube at the bottom so they're safe in snow, slush and mud), and everything locks up solid (and slides smoothly when not locked) in temperatures both hotter and colder than you can handle without a space suit. Oh, and you can do things with the legs and column that you simply can't do with other 'pods.

That still leaves finding a suitable head, but the case can be made that you don't really need a head with a Benbo (or any other tripod, for that matter) — it just makes fine positioning easier. A good three-way head may be better for extreme conditions than a ball head, precisely because the lock controls can be made larger and more positive while allowing for greater play in the mechanism. That's not to say that there aren't ball heads that are well-behaved and easy to use in the cold, but they do tend to be on the expensive side. The Benbo isn't Walmart cheap, but it's not tremendously expensive either, and a decent, positively-locking three-way with large knobs/handles can be had for a reasonable outlay as well.