Oktober is koud.

Because names of months in Dutch normally appear without an article.

• Oktober is koud. = October is cold.
• December komt snel. = December is coming soon.

You usually do not say de oktober or het oktober when simply naming the month.

Because koud is being used as a predicate adjective here, after the verb is.

In Dutch:

• before a noun, adjectives often take -e:
  de koude maand = the cold month
• after zijn / is, they usually do not take -e:
  Oktober is koud.

So:

• Oktober is koud. ✔
• Oktober is koude. ✘

It is grammatically correct, but it can sound a little less natural than some other options.

Dutch speakers often prefer:

• In oktober is het koud. = It is cold in October.
• Oktober is een koude maand. = October is a cold month.

Why? Because a month is not literally “cold” in the same way weather is cold. So Oktober is koud is understandable, but In oktober is het koud is often more idiomatic.

Because Dutch and English are closely related Germanic languages, and some very common verbs look similar.

Here, is is the third-person singular form of zijn (to be):

• ik ben = I am
• jij bent = you are
• hij/zij/het is = he/she/it is

So in Oktober is koud, is works just like English is.

No. In Dutch, names of months are normally not capitalized, unless they come at the beginning of a sentence.

So:

• Oktober is koud. ✔ because it starts the sentence
• In oktober is het koud. ✔ lowercase in the middle of the sentence

This is different from English, where October is always capitalized.

A simple learner-friendly guide:

• oktober ≈ ok-TOH-bur
  Stress is on the second syllable.
• is = short iss
• koud ≈ like cowd or kout, with the ou sounding roughly like the vowel in now

So the whole sentence is roughly:

ok-TOH-bur iss kowd

The Dutch r and d may sound a bit different depending on region.

Yes, and in many situations that is actually the more natural sentence.

Compare:

• Oktober is koud. = October is cold.
• In oktober is het koud. = It is cold in October.

The second version focuses more clearly on the weather during October, which is often how Dutch speakers naturally express this idea.

In this sentence, Oktober is the subject, so Dutch does not need het.

• Oktober is koud.
  Subject = Oktober

But if you use the more weather-like expression, Dutch usually does use het:

• In oktober is het koud.

Here, het is the dummy subject, similar to English it in It is cold.

The word order is very straightforward:

Oktober + is + koud
subject + verb + adjective

This is the normal basic pattern for a simple Dutch main clause.

You can compare:

• De soep is warm. = The soup is warm.
• Het water is koud. = The water is cold.
• Oktober is koud. = October is cold.

No, that would not be correct in normal Dutch.

Month names are used without an article when you mean the month itself:

• Oktober is koud. ✔
• In oktober regent het vaak. ✔
• De oktober is koud. ✘

Very unusual poetic or special uses aside, learners should treat month names as article-less in ordinary sentences.