Toen het buiten koud werd, voelde ik mijn benen rillen onder de tafel.

Because toen introduces a subordinate clause. In Dutch subordinate clauses, the finite verb usually goes to the end.

So:

• Toen = when
• het buiten koud werd = it got cold outside

Structure:

• Toen
  • subject (het) + adverb (buiten) + adjective/predicate (koud) + finite verb (werd)

This is very normal Dutch word order after conjunctions like toen, omdat, als, terwijl, and dat.

This is because of the Dutch V2 rule in main clauses: the finite verb must come in the second position.

Here, the first position is taken by the whole opening clause:

• Toen het buiten koud werd

After that, the main clause starts, and the finite verb must come immediately:

• voelde = second position
• ik = subject comes after the verb

So:

• Toen het buiten koud werd, voelde ik ...

If the sentence began directly with the subject, then you would get:

• Ik voelde mijn benen rillen onder de tafel.

Here toen means when in reference to a specific moment or situation in the past.

Dutch often uses:

• toen = when, for a specific event in the past
• als = when/if, often for repeated situations, general truths, or conditions
• wanneer = when, often more neutral or formal, sometimes more like asking at what time

So in this sentence, toen fits because the sentence describes a particular past moment:

• Toen het buiten koud werd... = When it got cold outside...

Because werd comes from worden, which here means to become or to get.

So:

• het was koud = it was cold
• het werd koud = it became cold / it got cold

The sentence is talking about a change: it was not cold before, and then it became cold. That is why werd is used.

Buiten can work as an adverb meaning outside or outdoors.

So:

• het is buiten koud = it is cold outside
• toen het buiten koud werd = when it got cold outside

You do not need a preposition here. Dutch often uses buiten directly as an adverb, just like English can use outside.

This is a common Dutch pattern with verbs of perception such as:

• zien = see
• horen = hear
• voelen = feel

The pattern is:

• perception verb + object + bare infinitive

So:

• Ik voelde mijn benen rillen.
• literally: I felt my legs shiver.

Here:

• voelde = felt
• mijn benen = my legs
• rillen = shiver / tremble

This is very similar to English:

• I felt my legs shake.
• I heard the baby cry.
• I saw him run.

Notice that Dutch uses the infinitive without te in this construction.

Because after a perception verb like voelen, Dutch usually uses the infinitive to describe the action being perceived.

So:

• Ik voelde mijn benen rillen. = I felt my legs shiver.

Using rillend would change the structure and would not fit naturally here.

Compare:

• rillen = to shiver
• rillend = shivering

In this sentence, Dutch wants the action itself: my legs shiver, not an adjective-like form.

Because after verbs like zien, horen, and voelen, Dutch normally uses a bare infinitive.

So you say:

• Ik hoor hem zingen.
• Ik zie haar lopen.
• Ik voel mijn benen rillen.

Not:

• Ik voel mijn benen te rillen. ✘

This is just like English, where you say:

• I hear him sing
• not I hear him to sing

Yes. In this sentence voelen means to physically feel/sense something.

Because it is followed by:

• mijn benen = my legs
• rillen = shiver

the meaning is clearly physical perception.

Dutch voelen can also refer to emotions in other contexts, for example:

• Ik voel me verdrietig. = I feel sad.

But here it is definitely about bodily sensation.

Because Dutch usually includes the possessive when talking about body parts in this kind of sentence, especially when the body part is the object of the verb.

So:

• Ik voelde mijn benen rillen. = I felt my legs shiver.

This is very natural Dutch. English also often does the same here.

In some other expressions, Dutch may use a definite article instead, but in this sentence mijn benen is the most straightforward and natural choice.

Yes, if only one leg were meant:

• Ik voelde mijn been rillen. = I felt my leg shiver.

But mijn benen is natural if both legs were trembling from the cold, which is probably the intended meaning here.

Rillen usually means to shiver, to tremble, or to shake slightly, often because of cold.

In this sentence, it fits very well because the first clause mentions that it got cold outside.

So the sentence links naturally:

• it got cold
• the speaker felt their legs rillen

That makes shiver or tremble the best sense here.

Because Dutch often places location phrases later in the clause, especially after the main action.

So:

• voelde ik mijn benen rillen onder de tafel

is a natural order.

The phrase onder de tafel tells you where the legs were shivering, or where the speaker perceived this happening.

Putting it at the end sounds smooth and unmarked. Dutch word order is somewhat flexible, but this placement is very normal.

Most naturally, it refers to the legs being under the table.

So the most likely reading is:

• the speaker was sitting at the table
• their legs were under it
• they felt their legs shiver there

Grammatically, Dutch can sometimes allow a phrase like this to attach a bit broadly to the situation, but in normal interpretation it belongs with mijn benen rillen.

Not perfectly. A very literal version would be:

• When it outside cold became, felt I my legs shiver under the table.

That shows the Dutch structure, but it is not natural English.

A natural English version would be something like:

• When it got cold outside, I felt my legs shiver under the table.

So the meaning matches closely, but the word order does not.

Yes. The het here is a dummy or impersonal subject, similar to English it in:

• It is cold outside.
• It got cold outside.

It does not refer to a specific thing. It is just required by the grammar of the sentence.

So:

• het werd koud = it got cold

works the same way as English.

Yes, that is possible, but Toen het buiten koud werd sounds more natural and neutral here.

Both are understandable:

• Toen het buiten koud werd
• Toen het koud werd buiten

The first one is the usual, smoother order because buiten naturally sits before koud werd in this clause.

Both are simple past forms.

• werd = past of worden
• voelde = past of voelen

So the whole sentence is narrating something in the past:

• first it got cold outside
• then the speaker felt their legs shiver

This is a very common storytelling tense in Dutch.

Yes. The comma separates the opening subordinate clause from the main clause:

• Toen het buiten koud werd, voelde ik mijn benen rillen onder de tafel.

This is standard punctuation in Dutch and helps make the sentence structure clear.