Gryffindor: Shoulder/back-of-the-neck burns. They thought they'd be fine going out for a fairly short amount of time and neglected to put on any sunscreen

Ravenclaw: Burns in big areas (like legs or arms). They don't put enough sunscreen on because they hate how long it takes to rub in when you put a lot.

Hufflepuff: Easily forgotten places, like the tips of their ears and the tops of their feet. They're good about sunscreen but sometimes forget more obscure places.

Slytherin: Burns on their back. They can't quite reach all the way to put sunscreen on back there and don't bother asking other people to help them.