As someone who once upon a time worked as a bike riding mailman in Sweden, it's largely fine. :)

There's a good amount of bike lanes, and they are largely snowy in the winter rather than icy (due to not as much traffic as the main roads), or they are graveled when there is ice, so it's rare that it is too slippery (biking on snow is fine, ice can be messy). You have to go a bit slower than normal, sure, but it's hardly a problem.

Cold isnt a problem - you do fine with like a fleece down to minus 10 or so, and most places aren't colder than that very often (unless you are very far north).

Rain is the same as anywhere - no problem as long as you have some protective gear.

Thats just the winter though - summer it is perfect.

I assume you talk about the winter?

If you live in a city, the bicycle roads will be plowed regularly. Get a wind stopping jacket and pullover for your trousers. Use two pair of gloves. (You will get warm from bicycling, don't use a too warm jacket.)

And use winter tires for the bicycle, they are pure magic.