Learn Hardcore Russian: После дождя воздух становится прохладным и лёгким. - After the rain the air becomes cool and light.

После чего? – после дождя (after the rain)
после работы (after work), после урока (after the lesson), после фильма (after the movie)

Saying после дождь would be ungrammatical, because the case after после must be genitive, not nominative.

Why are прохладным and лёгким in this form, and what case is that?

Прохладным and лёгким are in the instrumental case, masculine singular.

The pattern here is:

Subject: воздух (nominative)
Verb: становится (becomes)
Predicate (what it becomes): прохладным и лёгким (instrumental)

With verbs like быть (to be) and становиться / стать (to become), Russian very often uses the instrumental case for what the subject “is” or “becomes”:

Он был учителем. – He was a teacher.
Она стала врачом. – She became a doctor.
Воздух становится прохладным. – The air becomes cool.

So прохладным and лёгким answer the question каким? (what kind of?) in the instrumental: каким становится воздух? – прохладным и лёгким.

Why does one adjective end in -ым (прохладным) and the other in -им (лёгким)?

Both are masculine/neuter singular instrumental endings; the difference comes from the base form of the adjective.

Base forms:

прохладный → instrumental: прохладным
- Adjectives ending in -ый / -ой usually take -ым in masc./neut. instrumental.
лёгкий → instrumental: лёгким
- Adjectives ending in -ий usually take -им in masc./neut. instrumental.

So the rule of thumb:

-ый / -ой → -ым (новый → новым, холодный → холодным)
-ий → -им (синий → синим, русский → русским, лёгкий → лёгким)

That’s why прохладным, but лёгким.

Why do we use становится here instead of just saying “air is cool and light” with no verb, as Russian often does?

Russian can indeed omit быть (to be) in the present tense:

Воздух прохладный и лёгкий. – The air is cool and light.

But становится (becomes / is becoming) expresses a change of state, not just a description. It emphasizes the process:

Воздух прохладный и лёгкий. – Static description: The air is (now) cool and light.
Воздух становится прохладным и лёгким. – Dynamic: The air is becoming / gets cool and light.

In your sentence, после дождя implies a change happening after the rain, so становится is very natural.

Could we say воздух становится прохладный и лёгкий (adjectives in nominative), or is that wrong?

With становиться, the norm is to use the instrumental for the new quality:

✅ воздух становится прохладным и лёгким

Using the nominative:

❌ воздух становится прохладный и лёгкий

sounds ungrammatical or at best very non‑standard in modern Russian in this context.

So: with становиться / стать, use the instrumental for adjectives and nouns that describe what something becomes.

What is the difference between становится and станет here?

Both come from the same verb pair:

становиться (imperfective) – становится (he/she/it becomes, is becoming)
стать (perfective) – станет (he/she/it will become)

Nuance:

После дождя воздух становится прохладным и лёгким.
– Present tense, imperfective: general/habitual truth. After rain, (in general) the air gets cool and light.
После дождя воздух станет прохладным и лёгким.
– Future, perfective: one specific event, result. After the rain, the air will (then) become cool and light.

Your sentence sounds like a general observation, so становится is the natural choice.

Could we say После дождя воздух прохладный и лёгкий without становится? Would that change the meaning?

Yes, you can say:

После дождя воздух прохладный и лёгкий.

This is grammatically correct. The nuance:

становится прохладным и лёгким – focuses on the process of becoming cool and light after the rain.
воздух прохладный и лёгкий – just states the condition of the air after the rain, without highlighting the change.

In many contexts the difference is subtle, and both versions would be understood almost the same.

Can we change the word order to Воздух после дождя становится прохладным и лёгким? Is that still correct?

Yes, that word order is also correct:

После дождя воздух становится прохладным и лёгким.
Воздух после дождя становится прохладным и лёгким.

Both mean the same thing. The difference is what you highlight:

Starting with После дождя puts more emphasis on the time condition (“after the rain…”).
Starting with Воздух puts more emphasis on the air itself.

Russian word order is relatively flexible, especially when it doesn’t create ambiguity.

What does лёгкий воздух really mean? “Light air” sounds strange in English.

In this context, лёгкий воздух means something like:

fresh air
air that is easy to breathe
not heavy, not stuffy, not humid

So прохладный и лёгкий together give the idea of air that is cool, fresh, clean, not oppressive.

In English, you normally wouldn’t translate it literally as light air; more natural equivalents are cool and fresh, cool and crisp, cool and easy to breathe.

How is лёгким pronounced, and why does it often sound like there is an х instead of г?

Лёгким is pronounced approximately as [лёхким].

Two important points:

Stress and vowel
- Stress is on лё-: лЁгким
- ё is always stressed and sounds like [yo] / [ɵ] depending on accent.
Consonant change: г → х before к
- The word is built from the stem лёгк-
  - ending -им → лёгким.
- In fast, natural speech, the cluster гк is usually pronounced as хк:
  - лёгкий / лёгким → sounds like лёхкий / лёхким.

This is a regular phonetic simplification in Russian and doesn’t affect the spelling: you always write г, even though you often hear х.

Could we use short-form adjectives here, like Воздух лёгок и прохладен? How would that sound?

Yes, grammatically you can say:

Воздух лёгок и прохладен.

Here:

лёгок – short form of лёгкий
прохладен – short form of прохладный

Nuance:

Short-form adjectives are common in literary style, poetry, and more elevated or formal speech.
In everyday spoken Russian, people more often use the full forms:
- Воздух лёгкий и прохладный.

Also, if you keep становится, you normally don’t use these short forms:

✅ воздух становится лёгким и прохладным
❌ воздух становится лёгок и прохладен (sounds wrong to a native speaker)

Why is there no word for “the” in воздух or дождя? Shouldn’t it be “the air”, “the rain”?

Russian has no articles at all — no a/an and no the. The ideas expressed by English articles are usually conveyed by:

context,
word order,
additional words (like этот = this, тот = that),
or are simply left implicit.

So:

После дождя воздух становится прохладным и лёгким.
can be translated as:
- After the rain, *the air becomes cool and fresh.*
- or After rain, air becomes cool and fresh. (more general)

Russian doesn’t mark this difference grammatically; English has to choose an article in translation.