The air conditioner broke and our house was like a sauna! My sister-in-law beat the heat with a fan. But the weak fan didn't stop her sweat at all, so she lifted her skirt in front of the fan and flapped her clothes even though she wasn't wearing a bra, exposing her huge breasts! I got an erection without thinking and my sister-in-law noticed... This is bad! Just as I was thinking that, she reached for my erect penis! In the end, I was swept away by the atmosphere and we ended up having sex while covered in sweat!