Why do I sweat more than my family?

Okay, I sweat really easily. I’m serious! I live in East Texas and it gets HOT here. If I go outside for more than thirty seconds to a minute in the summer, my underarms get sweaty and I get itchy. I’m not even kidding, thirty seconds! It’s horrible because it’s too expensive to keep the house lower than 79 degrees and I get sweaty in the house! My sister’s boyfriend sweats a lot too. He says it’s because his body temperature is higher than the normal person. So, why do I sweat so easily?