Learn Hardcore Russian: Вчерашний дождь был ужасным, и на улице было холодно. - Yesterday’s rain was terrible, and it was cold outside.

вчерашний дождь treats the rain as a specific, already known rain (yesterday’s one).
дождь вчера был ужасным sounds more like you’re just stating when the rain was.

In this sentence, вчерашний дождь sounds more natural and compact, like English “yesterday’s rain.”

What case is ужасным and why is it used with был?

ужасным is in the instrumental case (masculine singular: -ым).

In Russian, when you use быть (to be) in the past or future and describe what something was / will be (a quality, role, state), you often put the predicate adjective/noun in the instrumental:

дождь был ужасным – the rain was terrible
Он был учителем. – He was a teacher.
Погода была холодной. – The weather was cold.

So:
дождь (Nominative, subject) + был (past “to be”) + ужасным (Instrumental, predicate describing the subject).

Can I say Вчерашний дождь был ужасный, ужасен, or ужасно? What’s the difference?

All are grammatical, but they differ in style and nuance:

Вчерашний дождь был ужасным.
- Instrumental predicate adjective.
- Very standard, neutral: The rain yesterday was terrible.
Вчерашний дождь был ужасный. (Nominative ужасный)
- Less common in careful speech; can sound more colloquial or emphatic.
- Grammatically possible, but learners are usually taught был + Instrumental (ужасным).
Вчерашний дождь был ужасен.
- ужасен is a short-form adjective.
- More expressive / literary: The rain was awful with a bit of emotional coloring.
Вчерашний дождь был ужасно.
- This is wrong in this context. ужасно is an adverb (terribly), not appropriate after был to describe the noun дождь.
- But you can say: Вчерашний дождь шёл ужасно долго. – Yesterday’s rain went on terribly long.

For learners, the safest neutral form here is был ужасным.

Why is there a comma before и in …был ужасным, и на улице было холодно?

In Russian, you normally put a comma before и when it joins two independent clauses (each with its own verb):

(Вчерашний дождь) был ужасным – complete clause (subject + verb).
(на улице) было холодно – another complete clause.

Because each part has its own predicate (был, было), Russian punctuation rules require a comma:

Вчерашний дождь был ужасным, и на улице было холодно.

If и joined just two words or phrases inside one clause (e.g. ужасным и холодным дождём), you wouldn’t put a comma.

Why is it на улице было холодно, not было холодным?

For weather and general states like it was cold, Russian usually uses an impersonal construction with холодно:

На улице было холодно. – It was cold outside.

Here:

холодно = an adverb-like predicate (often called a “category of state”).
было = neuter past of быть, used impersonally (there is no real subject).

Saying на улице было холодным would sound odd, as if “the outside” itself was a cold object. For temperature and weather, use холодно / жарко / тепло / сыро etc., not instrumental adjectives.

What grammatical gender is дождь, and how does it affect the sentence?

дождь is masculine.

This gender affects:

The adjective:
- вчерашний (masc. sg.) agrees with дождь.
- Feminine would be: вчерашняя ночь.
- Neuter: вчерашнее письмо.
The predicate adjective in instrumental:
- ужасным (masc. sg. instr.) agrees with дождь.
- Feminine: ужасной.
- Neuter: ужасным but with different noun, e.g. письмо было ужасным.
The past tense of verbs referring to дождь would also be masculine:
- Дождь начался. (The rain began. – masc. past).

So gender controls the endings of adjectives and sometimes verb forms.

Why is было neuter in на улице было холодно? What is the subject here?

This is an impersonal sentence: there is no real grammatical subject like it in English.

было is the neuter past of быть, used as a sort of “dummy” verb form in impersonal constructions.
холодно is the main predicate meaning cold (as a state).

You can think of it as:

(Было) холодно на улице. – It was cold outside.

There’s no noun in the nominative acting as the subject. The neuter было is the default past form used when there is no subject. This is very typical in Russian for weather, feelings, and states:

Было темно. – It was dark.
Мне было страшно. – I was scared / It was scary to me.

Could we reverse the order of the clauses, like На улице было холодно, и вчерашний дождь был ужасным? Does it change the meaning?

Yes, you can:

На улице было холодно, и вчерашний дождь был ужасным.

Both orders are grammatically correct. The meaning is essentially the same; you just change what you mention first:

Original: starts with the rain, then adds that it was cold.
Reversed: starts with the cold outside, then adds how bad the rain was.

Russian word order is flexible; changes often affect emphasis or flow more than basic meaning.

Why do we keep был / было here, when Russian often drops “is” in the present tense?

In Russian:

Present tense есть (is/are) is usually omitted:
- Дождь ужасный. – The rain is terrible.
- На улице холодно. – It is cold outside.

But in the past and future, the verb быть is normally used:

Past:
- Дождь был ужасным. – The rain was terrible.
- На улице было холодно. – It was cold outside.
Future:
- Дождь будет ужасным. – The rain will be terrible.
- На улице будет холодно. – It will be cold outside.

So you can’t usually drop был / было / будет the way you drop present есть.

How would this look if I talk about today’s or tomorrow’s rain instead of yesterday’s?

Russian has similar time-based adjectives:

сегодняшний – today’s
завтрашний – tomorrow’s

So you can say:

Сегодняшний дождь был ужасным, и на улице было холодно.
– Today’s rain was terrible, and it was cold outside.
Завтрашний дождь будет ужасным, и на улице будет холодно.
– Tomorrow’s rain will be terrible, and it will be cold outside.

Pattern:
вчерашний / сегодняшний / завтрашний + noun.

Why is it на улице (with на and prepositional case), and not something like в улице?

The phrase на улице is a fixed, very common expression meaning outside / outdoors / in the street.

Preposition на
- prepositional case улице:
  - на улице – outside / out in the street.

You almost never say в улице. в is used with улица mostly for motion (onto the street) or other more specific phrases:

выйти на улицу – to go outside / go out onto the street.
жить на этой улице – to live on this street (again на улице).

For weather / outdoor conditions, Russian normally uses на улице:

На улице холодно. – It’s cold outside.
На улице идёт дождь. – It’s raining outside.