"Life in Norway" has a description of traditions and celebrations of Christmas in Norway.: https://www.lifeinnorway.net/christmas-traditions-in-norway/
You may want to visit the first half of December in that Norwegians are more inclined to take family time during the Christmas week. We have not visited in December but have been to Norway during Easter. Basically most of Norway went on holiday during Easter Week including the Monday after Easter holiday. I would expect the same of Christmas week.
Julaften (Christmas Eve) is the day when presents are exchanged and
the whole family gets together for the main Christmas meal. Christmas
Day is a much quieter affair and often quite private.
This is followed by romjul. It's one of my favourite words in
Norwegian as it's only six letters long yet we don't have an
equivalent word in English! Simply put, it translates as: “that time
between Christmas and New Year when no-one is really sure what they
should be doing.”
Employees are often encouraged by their employers to take the period
of romjul off as part of their annual leave. Some may give bonus days
to reduce the amount of vacation days an employee needs to take from
their annual allowance.
On the other hand, the lead up to Christmas week sounds like a festive time of the year.
Christmas markets in Norway The festivities tend to get going in the
early part of December. That's when Christmas markets spring up in
towns and cities across the city. While snow is not guaranteed at this
time of year in many places, you are pretty assured of chilly
temperatures! That makes the spiced, mulled wine (gløgg) taste all the