I grew up in Sweden which means I grew up with a constant anxiety about the sun. If it was sunny outside, I had to go outside. It did not matter if it was warm or cold, the sun was all that mattered.
The reason I think we all have this stress about the sun is because we have so little of it. During the long and cold winter months, Swedes experience very little sunlight. In the Northern parts of Sweden there is barely any sun at all, and even in the most Southern parts - where I am from - sunshine is still pretty sparse.
This is also the reason you might see Swedes in Spring stop in the middle of the street and turn their heads towards the sun, just to get a little bit of that warming light. Or, freezing, whilst they are trying to enjoy a coffee outside in the middle of February, just because there is a little bit of sun.
So if you are wondering why your Swedish friends and colleagues force you to go outside every time there is a little bit of sun, now you know why!