At least it is only a 5 km. It is no different than skiing. Sometimes you are too warm when your are exerting yourself, but you sill need layers and something to cut the wind. With a wind chill of 5 at rest it will feel a lot colder when you are riding into the wind.
Here is a trick I learned running in the north. I would always go out into the wind so if it got too bad I could always turn around and run home with the wind at my back. I never had to do that despite running at temperatures as low as -35ºC.
Have fun.