Scrolling through I don’t see this tip I was made aware of when going up north: shower in the evening. I’m not sure it makes any significant difference, but the logic seems sound; while sleeing you build up a protective layer of fat on the surface of your skin, face especially. It helps against the cold, so don’t rinse it off in the morning.

Layers are important for your clothing. You don’t want to get too hot if you’re working outside. Breaking a sweat will make you freeze, so you need to be able to adjust throughout the day.

Northern scandinavian, here.
This depends on where specifically. Near the ocean it’s not that cold at the moment (well, depends what you’re used to, I guess. I get around fine with t-shirt and a light jacket. Temp varies between 5C and 15C nowadays.

But in general, I suggest you bring a sweater , some woollen socks, and a jacket that can handle rain/slush/snow. Staying dry means staying warm. Dressing with layers is better than one thick coat.

Snow will set in soon, though, so if you’re going to be working outside I recommend some gloves. Preferably two pairs, so one can dry off while you’re wearing the other pair.

May I ask where specifically you’re going? Coast vs inland makes A LOT of difference. Humidity can make 5C near the coast feel colder than -20C inland. Plus wind isn’t as much of a factor far away feom the ocean.

Northern Canadian here. Your worst enemy in the cold is wetness. As others have said, layers are key. Silk and wool are top of the list, but synthetics are okay, too. Silk and wool are expensive, synthetics are cheaper. Do NOT wear cotton. Cotton gets wet and stays wet. It truly sucks in cold weather.

Sweating makes you wet. You have to match your layering to your activity. If you are going to be active, don’t overdress. You should feel chilly when you first start your activity. A common trick is to layer up, then take off your parka to do physical activity, then put it back on when you are done with the activity. Some jackets have pit zips that you can open to shed excess heat. If you are going to sweat, plan it so that you end up indoors somewhere you can dry out. Don’t sweat and then plan to stand around or sleep outside.

If you are going to be mostly standing around, you need big, bad-ass Baffin-style boots, which are heavy. If you’ll be moving around, you can use insulated hiking boots and wool socks. Bring extra underwear and socks because they get wet.

Mitts and a touque are mandatory. Bring two sets because they get wet. Gloves are much less warm than mittens. You can layer that, too. A very thin synthetic glove inside of a mitten works when you need to take off your mitts to work on stuff. It is also worthwhile to get a thin, synthetic balaclava to help prevent wind burn and frost bite. Fingers, toes, and cheeks are the most susceptible to frost bite.

Grow out your beard if you are a dude.

In terms of less intuitive tips, as someone else said, if you start getting cold, expelling urine and faeces really does help. Also, stay hydrated. You get cold when you get dehydrated. You may not even feel thirsty, but cold air is dry air and you will get dehydrated quicker than you think in the cold. Especially if you are shoveling snow.

Shoveling snow sucks, so people tend to rush. The key is to go slow, especially if you are older. You will build up heat rapidly if you are shoveling. Avoid sweating too much, unless you have somewhere warm to dry off. Even if you aren’t shoveling, manhandling a snowblower will make you sweat heavily, too.