Breakdown of doushite kyou wa sonnani isoide iru ndesu ka?
Questions & Answers about doushite kyou wa sonnani isoide iru ndesu ka?
は marks 今日 as the topic: as for today.
So the sentence has a nuance like why are you in such a hurry today, specifically? It can sound as if today is a little unusual compared with other days.
A time word like 今日 can sometimes appear without a particle, so どうして今日そんなに急いでいるんですか is also possible. Using は just gives 今日 a bit more focus or contrast.
どうして is a common way to say why? or how come?
Compared with similar words:
- どうして: neutral and common in conversation
- なんで: more casual
- なぜ: more formal, more written, or more serious-sounding
So どうして fits very naturally in a polite spoken question like this.
そんなに means that much, so much, or to that extent.
Here it modifies 急いでいる, so it means something like:
- being in such a hurry
