Live in a house or apartment? In a house, sleep in the basement, it is usually a lot cooler.
When it gets really hot I take cold showers. After the first moment's shock, it feels great and you feel cooler for a long time after.
Avoid nicotine, it reduces your resistance to heat.
Eat very light, and avoid sugar and carbs, they burn hot for some reason. Eat small meals of protein and fat. Seriously, it helps.