There are many greetings in the world and depending on who you are saying it to, there many levels of formality.
This is no exception in Japan. There are of course the very formal greetings to superiors and older people, right down to the greetings of male work colleagues in the morning which at best sounds like a slightly aggressive snake. (I'm sorry guys, that's what it sounds like.)
In the summer, the common greeting changes from the usual, konnichi wa or ohayoo gozaimasu to the more season specific, ”暑いですねー” (Atsui desu ne) This literally means "it's hot."
OK, fair enough, it is 35 degrees celsius and 80% humidity, so yes it is hot. However in my opinion, if you say this, you are focusing on the heat and because of that you will feel hotter than if you were thinking about icebergs. (By the way, just by typing the word iceberg I felt cooler.)
I'm not just picking on Japanese speakers here. In English, we would say the same. We would probably use a couple of expletives here or there, for example, "F**k, it's hot." Of course we would feel hotter. Not a good thing.
Rather than focusing on the negative, i.e. the heat, why don't we focus on something like the weather. In other words, "It's a great day today, isn't it?"
Yep, it might be 35 degrees and 80% humidity but it is still sunny and nice, right? At least it isn't like the Arctic with snowy summers and polar bears wandering around town causing mischief.
So we should focus on the positive or not even talk about the negative. Why focus on it when you can put your mind to better things?
(This reminds me of the following song. Apparently my grandmother was determined that I would like this music and she would play it for me when I was in the cot. It must of worked because some go the songs in this movie are pretty cool.)