Coldest was -44°C when I was working as a northern lights guide in Norway. We'd always take our tour groups to areas with a high likelihood of polar activity, and once the whole coast was widely overcast so that we had to drive almost to the Finnish border. Camped out along the road towards Kilpisjärvi coming from Skibotn (company was based in Tromso).
Hottest was +45°C in Lagos, Nigeria. Used to work there as well for a good while.