Hi there! I don't think there's an idiomatic expression for that significance. But you can say "I'm heat intolerant" or "I suffer from heat intolerance".

But that's the point in reading a book in your target language. Sometimes you can understand an unknown term because the context gives you the idea, but if the word is constantly repeated then you should look up the meaning, so that the next time you see it, you'll easily remember it and therefore you'll have added up to your vocabulary. Keep on the good effort!