Those sentences may be examples of African-American Vernacular English (AAVE), a dialect of English spoken by black people mostly in the US. (However not all black people here speak this dialect, and some switch between dialect and "standard English" depending on the situation.) I'm no expert in this dialect, however it does have a grammatical structure. I'm not super familiar with how the grammar works but I will do the best I can in explaining the sentences. Some people may not consider this form of English to be "proper" or "correct", so there may be some confusion when it comes to this topic. But many people do communicate in this way and it works perfectly well. In your examples, the word "do" would likely be emphasized when speaking. 1) It do be hot here. It really IS hot here. 2) She do be -ing. She do be gettin' tan. She really IS getting tan. Or She really HAS gotten tan. 3) It really do be like that sometimes. It really IS like that sometimes. Or It really CAN BE like that sometimes.

This is almost certainly African-American vernacular English. It is a usage called the "habitual 'be.'" For a discussion of it try a web search on "habitual be wikipedia". I don't speak AAVE myself and I'm not very familiar with it, but I think the meanings are: 1) This is a place where it is usually very hot. 2) XYZ-ing is a habit of hers. 3) There are long periods of time when it is like that.

Colloquial slang considered improper for (It is) or (It does).