This is a good question and yes there is a difference. Fat is an insulator, it's why marine mammals that live in cold waters are sheathed in it.

Fat is adaptive in a cool climate because it reduces heat loss. In a warm climate it's a liability.

However, the body has a deep history of adaptive response to heat. As Mitch mentioned, one of the symptoms of heat stress is mild nausea.

This is absolutely true. If you want to lose 20lbs move to the tropics and live without AC. You will lose weight although it isn't a pleasant experience.