热死了
We usually usw this short sentence to express we feel very hot...but e don't really die...in Chinese we usually use '死了' after some adjectives to exaggerate..
e.g. 烫死了, 丑死了, 冷死了, 吵死了
usually these adjectives are talking about uncomfortable feelings. So painful that I am dying...: ) exaggeration
If you are talking about somebody dies from heat, we say 死于高温天气, more formal, 热死 more casual