Can someone say:
"ここに暑いですね?"
To ask: "Its hot in here, isn't it?" Or is the correct way to say it:
"ここで暑いですね？"
2 Answers
The usual thing to say would just be
暑いですね。
But if you to want to use ここ, I would say
ここは暑いですね。
ここが is also grammatically correct, though the emphasis is different. Neither に or で are appropriate here. に is typically used for a directional noun (though it is also used with things you might not think of direction, such as 住む), and で is usually used for where an action happens (well, it has other uses as well). Here there's no action happening, or a direction for it to happen in.
If you want to say "in here" (as in, in this room) rather than just here (which is all ここ means) you might say
このなかは暑いですね。 or このへやは暑いですね。
Neither で nor に is correct. Both sound highly ungrammatical here.
The only grammatical solution is to use は.
ここは暑いですね。
Or maybe better: この中は暑くないですか？
As you might have learned, Japanese is said to be a "topic-based" language. What this means is, in many cases, you have to first indicate the topic of the sentence using は. In this case the topic is about "here", ここ.
By the way of course there are cases "here" should be translated as ここに or ここで. Like:
[本棚]{ほんだな}はここに[設置]{せっち}します。 The bookshelf will be installed here.
あなたたちはここで待っていてください。 You please wait here.
In these cases ここは never occurs, because the topics are "the bookshelf" and "you", not "here".
In contrast, your example has no topic other than "here". (Even in English, the subject "it", which is often called a "formal subject", virtually means nothing.)
So, you have to attach は to the topic ここ in this case.
