The bow river isn't really any better during winter than the rest of the year (fishing wise), the fish are just holding in different water and there tends to be a lot of them congrugated in those waters. Its one thing to say I'm going fishing in -5 but getting out there is another story. The coldest day I fished in was -15 last year and it was definitely tough. Freezing guides, frozen reel, frozen waders, and the worst frozen laces, I couldn't get my boots off for a while, I had to melt the ice off with my lighter. You must also have to think of all the hazards while fishing during the winter months. Frostbite is an easy one, stripping in wet line can get you fingers pretty cold pretty quick. You also have to be aware slips, as snow starts to collect on your felt on your boots, any bit of ice seems like you just stepped on some serious slick oil! Chunks of ice floating down the river as well can be very hazardous, as if your not paying attetion and a large peice of ice comes floating right at you, you can find yourself in some trouble.
But anyway if you do head out dress warm, wear thermals if you got them and as for your hands go and buy some of those glove warmers and keep them in your either in your gloves or in your pockets. And there allready seems to be some good fishing tips on here so I'll leave it at that.