Learn Hardcore Russian: В северной части города обычно холоднее, чем в южной. - In the northern part of the city it is usually colder than in the southern part.

Underlying structure is roughly: (Здесь) обычно (есть) холоднее…
The verb есть (present of быть) is omitted in modern Russian in the present tense.

So В северной части города обычно холоднее literally behaves like “In the northern part of the city usually colder,” but is understood as “it is usually colder…” The “it is” is simply implied and not said. This is very common in descriptions of weather, temperature, states, etc.

What case are северной and части in в северной части города, and why do they have those endings?

They are in the prepositional singular, because of the preposition в indicating location.

часть (part) → prepositional singular: в части
северный (northern) must agree with часть (feminine, singular), so:
- feminine, singular, prepositional: северной

So в северной части = “in the northern part.”
The ending ‑ой on северной and ‑и on части reflect “feminine, singular, prepositional” agreement.

Why is it города and not городе after части?

Because часть (“part”) normally governs the genitive case for the thing it is a part of:

часть чего? – “part of what?”

So:

часть города – “part of the city” (города = genitive singular)
Put that into a prepositional phrase with в:
- в части города – “in the part of the city”
- with an adjective: в северной части города

If you said в северной части городе, it would be ungrammatical, because городе would be prepositional, but here we specifically need genitive after часть.

Why do we use в in в северной части and в южной, not на?

Both в and на can translate “in/on/at,” but their use is partly idiomatic.

Here:

в части is the normal combination: you say
- в части книги – in part of the book
- в этой части города – in this part of the city

So в северной части города is the natural choice.

With the nouns север / юг themselves you often get на:

на севере города – in the north of the city
на юге города – in the south of the city

So:

в северной части города ≈ на севере города (same idea, slightly different wording).

What is the difference between в северной части города and на севере города / на юге города? Are they interchangeable?

They’re very close in meaning, but not identical in feel:

в северной части города
- slightly more “geometrical/administrative”: “in the northern part/section of the city”
- hints at a division into parts (north, south, etc.), like on a map or in urban planning.
на севере города
- a bit more geographic, “in the north (area) of the city”
- doesn’t explicitly mention “part,” just “the northern side/area.”

In most everyday contexts you can freely say either:

В северной части города обычно холоднее, чем в южной.
На севере города обычно холоднее, чем на юге.

Both sound natural; the second is a little simpler lexically.

In чем в южной, what is южной referring to? Why can the noun be omitted?

Here южной is standing for южной части города (“the southern part of the city”). Russian often omits repeated words that are obvious from context.

Full, non‑elliptical version:

В северной части города обычно холоднее, чем в южной части города.

Because части города was just said once, it’s clear that в южной means “in the southern (part of the city),” so the noun phrase can be dropped. This kind of omission to avoid repetition is very common and stylistically normal.

What exactly is холоднее grammatically? Is it an adjective or an adverb? How is it formed?

Холоднее is the comparative form of the adjective холодный (“cold”).

Base adjective: холодный
Short/synthetic comparative: холоднее – “colder”

Grammatically:

Historically it’s a short-form comparative adjective, but
In sentences like this (with no explicit noun), it behaves like a predicative word, similar to an adverb:
- Здесь холодно. – It is cold here.
- Здесь холоднее (чем там). – It is colder here (than there).

It doesn’t change for gender or number: you always say холоднее, regardless of what is “colder.”

Could we say более холодно instead of холоднее? Is there a difference?

You can say более холодно, but холоднее is more natural and idiomatic here.

холоднее – simple, everyday comparative, default choice.
более холодно – “more cold”; feels:
- a bit more formal or bookish in many contexts,
- often used when:
  - the base form is clumsy to compare synthetically, or
  - you need to compare multi‑word expressions.

Here:

В северной части города обычно холоднее…
sounds simpler and more natural than
В северной части города обычно более холодно…

Why do we use чем after холоднее? Could we instead use a genitive like in Он старше брата?

Russian comparatives allow two main patterns:

Comparative + чем + same case as required by its own preposition
- холоднее, чем в южной части города – colder than in the southern part of the city
  (here в still governs the prepositional: в южной)
Comparative + noun in genitive (no чем)
- Он старше брата. – He is older than (his) brother.
- Это выше дома. – This is higher than the house.

But with adverbial comparisons like “colder there than there,” especially when you already have a preposition (в северной части, в южной), чем is by far the most natural:

В северной части города холоднее, чем в южной. ✔
В северной части города холоднее южной части города. ✖ (sounds wrong/unnatural)

So here чем is basically required to connect the two locations you’re comparing.

Why is there a comma before чем in холоднее, чем в южной? Is that comma always necessary?

In modern Russian, with чем in simple comparisons, the comma is often optional:

В северной части города обычно холоднее, чем в южной.
В северной части города обычно холоднее чем в южной.

Both are acceptable and used.

Rough guideline:

When the comparison is short and tightly bound, many writers omit the comma.
When the author wants a slight pause or when the comparison part is longer/clearer as a separate segment, a comma is inserted.

In textbooks and cautious writing you’ll often see the comma, as in your sentence; you don’t have to treat it as absolutely mandatory in constructions like this.

Where can обычно go in this sentence? Are other word orders possible and natural?

Yes, word order is flexible. All of these are grammatically correct:

В северной части города обычно холоднее, чем в южной.
– neutral, very natural.
Обычно в северной части города холоднее, чем в южной.
– puts emphasis on “usually,” like “Usually, in the northern part…”
В северной части города холоднее обычно, чем в южной.
– possible, but sounds a bit less natural; обычно feels slightly displaced.

The most common are (1) and (2). Russian adverbs like обычно can move around, but they usually stay near the verb or predicate word they modify – here that predicate is холоднее.

How should I pronounce the key Russian words here? Where is the stress?

Approximate stresses (stressed syllables in caps, Latin‑like transcription):

северной – СЕ‑вер‑ной → SÉ‑ver‑noj
части – ЧА‑сти → CHÁ‑sti
города – ГО‑ро‑да → GÓ‑ro‑da
обычно – о‑БЫЧ‑но → a‑BYCH‑no (with Russian ы)
холоднее – хо‑лод‑НЕЕ → ho‑lod‑NYÉ‑ye
южной – ЮЖ‑ной → YUZH‑noj

All unstressed о are pronounced more like a short a in normal speech (e.g. города ≈ GÁ‑ra‑da).