Yet, SMHI (the Swedish Meteorological and Hydrological Institute) doesn’t want to proclaim spring. How can it be spring if it hasn’t even been winter? No, the idea is that it is still fall in those places in Sweden. At the end of December, in Stockholm the average temperature is on the top 15 list with balmy December months (they began jotting down temperatures in 1756), with a 24-hour average temperature of 2.5 C (36.5F).