Getting sunburned for the first time in a really long time...?

So I am 20 years old, and I'm of Mocha color, typically. I am Peruvian-born, of a very mixed ancestry, Irish, German, French, Spanish, Incan, etc( from great-grandparents).

Essentially, I got a red tank top tan two days ago, from spending one day out with my lil bros and then driving around with some buddies in a convertible... and it was the first time this has happened to me basically ever, when i was 8 my family spent a full week in a beach town and i was there pretty much from early until the sun left and after 5 days my back was super dark and started peeling. That was the only other time I remember happening to me. It just seems very odd that after a lifetime of just getting tan, and tanner in the sun, I randomly would get redness and slight discomfort. Does anybody have any reasoning or theory on why this might be occurring now?? At first I thought it was the lack of slow tanning I used to get in high school through sports, but I've been out for 3 years and its the first time this has occurred, i've also been going to the beach pretty regularly. Another potential reason I thought might be that it was two days before the summer solstice which might have made the sun stronger, but i have no idea. Any feedback or actual reason behind it is much appreciate it