I'm not sure that people downvoting you have been around northerners much. Down here in the upper midwest US, we tend to consider 4 or 5C to be shorts weather in the spring. I've a friend who would wear flip flops / sandals outside down to roughly -10C.
Then again, most people aren't getting the equivalent of 15 minutes of index 7 UVB exposure at those temperatures, so it's not quite the same thing, but still.
