Winter Training

Dress warm.  The comfort zone for horses is between 15 and 50 degrees.  NO reason not to ride right through to spring as long as the ground isn't slick.

I ride in the winter.  It gets pretty dang cold here too!  Just bundle up.  I have a "buff" (one of those fabric tubes, like they have on Survivor) that I use to cover my nose, mouth and top of my head under my helmet.  I find it's less bulky and I get better coverage than a scarf.  I can fit my feet into my riding boots with wool socks on but they also sell winter riding boots too.  Thin gloves.  Long johns under my jeans (I really like Cuddle Duds b/c they're super thin but very warm) and a heavy winter jacket (I have a carhartt for the barn).  I really hate being cold so I bundle up really well... usually when brushing and tacking/untacking I don't wear my jacket, just a long sleeved tshirt with long johns top under since I work up a bit of a sweat then. 
I try to stick to beaten trails especially in areas where there are deep ditches that get filled in with snow.  At my old barn the owner made some little paths with his tractor that we would use otherwise the deer did a pretty good job of carving "highways" too.

What I have done in the winter is has one of the horses haul wood up to the house.  I just tie a rope on a log, put the loop on the saddle horn and ask them to walk forward.  I have also used a deer sled to drag hay bales in the past, that is, until my husband ran over the sled with the truck one day.
 
You would be surprised how much good it does just to put a saddle on a horse in the wintertime.  You don't have to ride.  I ride quite a bit on the gravel roads in the early spring because my training pen is too muddy to use.  We have had 40 degrees below zero windchills and I have still rode on occasion.  Luckily a little time in the round pen come spring does wonders.  I also might tie the horse up with the saddle on.  You can do this year round.