It is not true that 'almost all westerners' think this. 'Hot' is the opposite of cold.
Among English speakers, the only people who would pretend to misunderstand 'I'm so hot' are those who
.... have an immature sense of humour
... are overly influenced by American teen media
You could avoid the issue by using the impersonal construction with 'It is', if you wish, by saying 'It's so hot here/today/now', but it isn't necessary.