I grew up in a small town on a sea shore with hot and sunny summers (up to 30-35 degrees Celsius). I remember myself, my friends and relatives being outdoors for 12 hours a day. We never needed sunscreen, and never used it. It was considered, that skin can burn on first day of taking a sunbath and precautions were taking, i.e. "put long-sleeved shirt on after 3 hours under direct sunlight". Coordinates of my home town are 46°45′35″N 36°47′04″E. Currently, I live in another town, very close to an ocean shore, with coordinates 41°4′9″N 73°51′35″W, and we have hot and sunny summers (up to 30-35 degrees Celsius, sometimes a little bit more). I am very surprised how aggressive sun is here. We need sunscreen all summer long, and once I had to work outdoors for 8 hours at the beginning of September, and I somehow got a sunburn. Given my childhood experience, it would be impossible for me to imagine, that I could get a sunburn at the end of summer. I simply used to get a very nice suntan over summer, and then my skin was resistant to sunburn. I wonder what is an explanation for this. Explanation number 1 could be that sun is more aggressive in my current town, than it was in my home town. But why? Another explanation, that there are some other factors involved, but I am not sure what these factors could be. If anyone knows what is an explanation for this phenomenon, I would be most grateful for your help.