Middle and Northern Climate Zones. The middle and northern regions of Sweden have a humid, snowy climate. For fewer than four months a year the average temperature is above 50F (10C). February is the coldest month, ranging from -7F (-22C) to 27F (-3C) in the middle region.In northern Sweden, it can get down to -22F (-30C).lthough precipitation is higher in summer than in winter, Sweden is humid year round. Keep waterproof clothing available all year. For the warmer months, lightweight clothing is appropriate with extra layers available for the cool evenings. For the colder months, layers of medium-and heavy-weight clothing work well.