Learn Hardcore Japanese: natu no asa ha hayai desu.

は marks the topic of your statement (“as for…”). By saying 夏の朝は, you introduce “summer mornings” as the topic, then describe them as early.

If you used が:

夏の朝が早いです
you’d be marking 朝 as the subject and putting slight emphasis on the fact that “it’s mornings that are early,” as if identifying which thing is early. It’s not wrong, but changes the nuance from making a general comment to pointing out a specific subject.

What type of adjective is 早い, and how do you know?

早い is an い-adjective (i-adjective). You can tell because:

It ends with い in its dictionary form.
It can directly modify nouns: 早い電車 (an early train).
It conjugates by dropping or changing い:
- Negative: 早くない (not early)
- Adverbial: 早く (early/quickly)

Why is です needed at the end? Can I omit it?

です is the polite copula, making the sentence courteous.

In polite or formal contexts, keep です: 夏の朝は早いです.
In casual speech or writing, you can drop it: 夏の朝は早い。

Why is the word order 夏の朝は早いです and not 早いです、夏の朝は?

Japanese basic sentence structure is:
Topic (or Subject) → Object → Verb/Comment.

Here you have:
夏の朝は (topic) → 早いです (comment).

Putting the comment first (早いです) before introducing the topic (夏の朝は) would break this natural flow and sound very unnatural in Japanese.

Could we say 夏は朝が早いです? Is it the same meaning?

Yes. 夏は朝が早いです is a more common phrasing. In this structure:

夏は marks “summer” as the topic.
朝が marks “mornings” as the subject.

Both sentences mean “In summer, mornings are early.” The difference is purely how you distribute topic vs. subject:

夏の朝は早いです treats “summer morning” as one unit topic.
夏は朝が早いです treats “summer” as the topic, then “mornings” as the subject.

How do you say “early morning” in Japanese? Is it 早い朝?

早い朝 is understandable and grammatically correct.
The more idiomatic noun for “early morning” is 早朝 (そうちょう, sōchō).

Example:
早朝の散歩 – “early-morning walk.”