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.
The fact that I work with IT with a niche skill set that is highly sought after in my industry. I was 10 in 1993, and at that point I didn’t even know how to turn on a computer.
What I did use a lot, on the other hand, was my NES. And 10 year old me would probably make a jaw drop induced crater upon seeing the kind of games I can play nowadays. Hell, by brand new laptop is fancy on its own.