There's an vietnamese old belief to eat warm foods when it's hot out. I'm not quite convinced though, I'm sweating more my head plunged in my Pho Bo Vien (= a vietnamese noodle soup with meatballs). Another belief is people tends to eat less when hot weather. Again not sure. My belief is when Pho Bo Vien is for dinner, I can eat for a week, 3 times a day. No kidding!