Stockholm's northern geographical location on the earth results in short days and long nights in the winter. Conversely, during the summer months, Stockholm experiences very long days of sunlight. I've heard that in some parts of Sweden, you might go to sleep with the sun up and wake up with the sun up!
From what I know, Stockholm's environment has actually played a big role in aiding its sustainability efforts. The wide availability of water has led to the development of hydropower technology by Swedish scientists in harnessing its potential as a clean energy source. In addition, the drastic difference in daylight hours has led to the development of improved technology that optimizes the capture and storage of solar energy. The inconsistent hours of sunlight have driven researchers to find ways to create technology that allows collectors to work even when there is no direct sunlight available. In addition, all the surrounding nature provides many opportunities for activities such as hiking, kayaking, boating, jet skiing and ice skating, just to name a few.
From what I've gathered, I would say that the cold and extremely short days in the winter present a substantial challenge to the locals. In the heart of winter, which occurs in January and February, the average temperature drops to 24° F. During this time, daylight is only available for five hours, between the hours of ten a.m. and three p.m. Furthermore, this "daylight" is primarily cloudy and dreary and it becomes quite rare for one to catch a glimpse of the sun.
