Well treeslayer, i wish you good luck and it should be fun. I've worked with several southern boys who try a northern winter, and it's always interesting. Some thoughts, if i may:
You are going to be at a handicap right off the bat, just in the way you think. Those of us born and raised in cold and snowy winters look at it differently than you probably do. I remember as a kid and teenager sitting out in rich stadium for hours at a time in sub zero weather and having a great time watching the game. You've got to come to grips with the fact that a 20 degree day is a heat wave and by february you are praying for 20 degrees but count yourself lucky if it gets above zero. I think it helps being used to cold winters. Waking up to months of single digit temps or lower can be a depressing experience. Plus some people just prefer the cold-i'd rather work in 20 degrees all year around than 80 degrees. This means that probably what I work in all winter long would be worthless to you. Plus, i'm not sure how much snow you are going to get, but dealing with a couple feet of snow and cold temps is a whole different animal than just straight cold.
Alot of what was said here about layers is golden. However, you need to plan your layers for ease of "access." It can be annoying trying to grab "little treeslayer" through five layers of clothes when it's cold and he doesn't want to poke his head out. I've seen more than a few guys pee down the front of themselves. Laugh it up, but i'm not joking. If you have to actually take clothes off in order to take a leak, there is a problem. Plan your layers accordingly.
I like to climb cold. Meaning if I'm standing at the bottom of the tree and i am comfortable, i take a layer off. Getting up the tree and getting to work will get the blood pumping and it's easier to take a layer off on the ground. About the only time this will backfire is on really windy days-getting above the houses and letting the wind have a clear shot at you will cool you down quick. Once i'm up a tree, i stay moving. If waiting for the groundies, i'll fidget or swing around-anything that will keep my blood pumping and keep me warm. This also means i don't stop all day long. I've always hated lunch breaks. By lunch time, no matter how cold (and i've climbed in -40 in canada back in the 90's), i'm usually feeling comfortable. I've got my layers right, I'm hustling enough to keep the sweat down and keep the blood pumping. Then you stop. Sit in the truck, eat a sandwich. Start back up again and have to put layers on because the truck's warmth doesn't stay with you, then have to take layers off because you start sweating. No lunch breaks eliminates the hassle. Eat a big breakfast, have a power bar in the tree if hungry.
Heat at home--working a ten hour day in the cold will wear you down. You may ask, "but the days are shorter, you can't work ten hours." Ha, ha, all the crews i've worked with, shorter days only means you spend more time chipping brush by streetlight. You will want warmth at home. I grew up with a woodstove-these radiators, and baseboard heating , and radiant heat are horrible for warming up after a long day. Not to mention they do nothing for drying out clothes and ropes (more on this in a minute.) Get an electric blanket. Get a dryer. Nothing worse than starting a day with damp clothes. And ropes, bring them in EVERY night. Drag a rope through wet snow all day, freezes up at night, makes the next morning a real joy.
Feet: Warm feet are necessary-don't skimp on boots. You aren't going to be walking all day, so you need something insulated. JPS's layered socks is a great tip, but if one pair of socks makes your boots tight, go up a half size and wear a couple pairs. I don't know if it's true or just in my head, but a boot tight on the foot seems to keep my feet colder than one a little loose. As for steel toes, they've never bothered me but some people swear they are colder. Wesco insulated have always done the job for me. Tall socks, tall boots, jeans tucked into the boots to keep drafts down.
Legs: Cold doesn't bother my legs that much. I'll climb in jeans into the teens, then throw on a pare of noninsulated carhart bibs. That gets me down in the negative teens no problem. But like I said earlier, that is probably worthless to you. The big thing for me is keeping the pants dry. Snow is a killer. I'd rather climb in snow at 15 degrees than snow at 30 degrees. If you are going to be climbing in snow at a melting temp, throw another set or two of clothes in the truck. You will be frozen once the sun goes down if you stay in the wet clothes.
Torso: This is going to go against what everyone says here, but I love sheatshirts (not so much in 25+, but anytime below that.) I was downright shocked when someone here said they hated hoods. Around here for many years, climbers would sell their firstborn child for a couple asplundh or davy hoodies with the "grim reaper hoods." Then arborwear started making them. I love them-i'll climb all winter in a hoodie. The lightweight ones for 20ish, the heavier ones for lower temps. Cotton may kill, just don't get it wet from either the inside or outside and i've always been comfortable. But i wear them mainly for the hood, which brings me to...
Headgear: If you are working for a reputable company, they will probably make you wear a helmet or hard hat of some kind. The wind blowing up the back of most helmets is uncomfortable to say the least. There seems to be three main ways to wear a hard hat and stay warm that i've run across. (There's probably more, these are just the common one around here.) The hard hat liner is popular. I've never liked them, unless you get the ones with the longer necks. Wearing a stocking hat with a hard hat on top works but it's hard to keep the hard hat on. And using an oversized hood that will go over the top of the hardhat. The hood is what most use. We may look like dorks, but we are warm headed dorks. And I've never had a problem with being able to see. The "grim-reaper" hoods are made to go over hard hats. If it gets really windy, pop up the hood, throw a scarf in front of the mouth, and snug as a bug. Ear muffs are also a must. (Ear muffs are amazingly warm.)
Hands: I hate gloves-used to go as long as I could before it was unbearable, but now have a couple finger joints a bit messed up from it. My problem is big hands. Finding a good fitting glove is very hard for me. I ended up getting a local amish guy to custom make them for me. They are actually insulated gauntlets. I hate wide cuff gloves, they collect sawdust like crazy and within a couple days all your finger tips are packed. Plus they seem to pack with snow. Pig skin is the best leather, not quite a durable as cowhide, but drys faster and won't stiffen up as bad. But they only get pulled out when the temp is single digits. Leather gloves are horrible for wet snow. I've got some insulated smurfies that seem to do the trick for me. Also, don't underestimate a mitten. I spent enough time on open cabs as a teenager to realize the value of a mitten. I'll often wear them when chipping. Take several pair of gloves with you every day.
About the only other thing i can think of right now is breathe through your nose. Hustling around all day gulping in air through your mouth will make your evenings unenjoyable.
