Should Quotation-Ending Period Be Comma Unless Sentence Ending?

Now I’m checking Quotation Marks article by Grammarly. The article, for example, introduces

“There was a storm last night,” Paul said.

which uses a comma at the end of the quoted sentence, and

John said, “I really hate when it’s hot outside.”

which uses a period instead. Because the article doesn’t tell, I wonder whether the period at the end of the second example—even if it is a sentence-ending period—must be changed to a comma if I invert or extend the sentence as follows.

“I really hate when it’s hot outside,” John said.

or

John said, “I really hate when it’s hot outside,” but it seemed his dog didn’t.