"It is hot today."
The English "it" when describing weather conditions is a dummy pronoun (it doesn't refer to anything in particular) so its translation will depend on what the other language requires. Think of "it rains", what does? You're not particularly referring to a cloud or the sky.
Different languages use different structures, and some of them make no sense whatsoever (Spanish uses "to make" or "to do": "Hace calor"). To the subject, Ukrainian doesn't need to add any extra words: just saying "today" and "hot" does the trick.