I love brewing outside in the winter. All that free ice in the form of snow for recirculating the cooling water. I'm lucky though that I have a wash tub inside that has a faucet I can hook my hose to. So, I do all my filling of water from there. I mash in my cooler in the kitchen and it's a short few steps to the garage from there. I'll take brewing on a 20 degree day over a 90 degree day any time. Plus, not having to worry about bees, wasps, falling leaves and flies is awesome.
Usually if it's above 20, I just go ahead and hook up my hoses outside. Just make sure you don't leave them connected when not running water through them. The key is to get yourself a spare hose you keep inside during the winter. So You don't have to deal with frozen rubber as well.