You can find some information on the trend of activity, but that’s about it. There’s no real rhyme or reason. It may happen every day for 2 weeks or go 2 weeks without seeing it. Generally, though, you’re in a downward cycle, so they will likely be less intense and few of them overall.
Your best bet it to rent a car and cross over into the far north Finnish border in the Kilpisjärvi area. Because of its location, the climate is clear and dry. You won’t have to contend with the same issues as far north Norway. If you have access to cabins in the northern fjords, that would be great as well.
Let me know if you want a connection - I know a number of people with cabins about 3 hours north of Tromso and I know they sometimes rent them out.