Hi Pete,
Enjoyable - and extensive - trip write up. Great effort and thanks for sharing.
And just to chip in on the temperature debate - we were up north of Gallivare that same week and the days you had the cold temps in Jokkmokk the temperature where we were was minus 20 to 25 during the day and around minus 30 to 35 at night. We weren't using a low-reading thermometer but the coldest we noticed was minus 37.
One of the most reliable sources for weather in this area from the Swedish Institute of Space Physics.
The IRF weather data includes historical temperatures as well as real-time (it's currently -26 Celsius as I write this).
You can see current data on this page here:
http://www.irf.se/weather/
You can click on 'temperature', 'moisture', 'pressure' etc to get detailed historical data.
All the best,
Paul