Sweden is big country for its population size and has some of the best trails for MTBing and can satisfy any randonneur ...however in winter time, most of the trails are covered with snow and too dangerous though I have biked even during those months but it is quite challenging even with winter tires. But the fatigue factor goes up 4-5X so if you were to do 100 miles in summer, in winter you won't be able to do more than 15-20 miles
What about the roads in the city? Safe or icy?
Cheers, Doc