Сегодня гололёд, поэтому я надела зимние ботинки.

In Russian, the verb to be is usually omitted in the present tense.

So:

• Сегодня гололёд = Today, there is black ice / it’s icy today
• literally: Today black ice

This is completely normal in Russian. You also see the same pattern in sentences like:

• Сегодня холодно. = It’s cold today.
• У меня отпуск. = I’m on vacation / I have vacation.

So the first clause is natural even without a verb.

Гололёд means icy conditions, black ice, or a slippery ice layer on roads and sidewalks.

It is not just ordinary ice in the general sense. Compare:

• лёд = ice
• гололёд = black ice / icy conditions

So Сегодня гололёд suggests dangerous, slippery weather rather than just the existence of ice somewhere.

Поэтому means therefore, that’s why, or so.

In this sentence, it connects the cause and the result:

• Сегодня гололёд = cause
• поэтому я надела зимние ботинки = result

The comma is placed before поэтому:

• Сегодня гололёд, поэтому я надела зимние ботинки.

That punctuation is standard in Russian when поэтому connects two clauses like this.

Because the verb is in the past tense feminine singular.

Russian past tense changes for gender in the singular:

• я надел = I put on (speaker is male)
• я надела = I put on (speaker is female)
• я надело = neuter, used only for neuter subjects, not я
• мы надели = we put on

So надела tells you that the speaker is female.

This is a very common question.

• надеть = to put on something on yourself or onto someone/something
• одеть = to dress someone

So:

• надеть ботинки = to put on boots
• одеть ребёнка = to dress a child

A useful memory trick:

• надеть что-то = put something on
• одеть кого-то = dress someone

That is why я надела зимние ботинки is correct.

In Russian, footwear like boots, shoes, and socks is very often simply used in the plural:

• ботинки = boots / shoes
• сапоги = boots
• кроссовки = sneakers

So я надела зимние ботинки is the normal way to say I put on winter boots.

If you really want to say a pair of boots, you can say:

• пара ботинок

But in everyday speech, just using the plural noun is much more common.

Because ботинки is the direct object of надела, so it is in the accusative case.

However, for inanimate plural nouns, the accusative looks the same as the nominative.

So:

• nominative: зимние ботинки
• accusative: зимние ботинки

That is why the form does not change here.

Compare with an animate plural noun, where the accusative would look different:

• nominative: новые студенты
• accusative: новых студентов

Since ботинки are inanimate, зимние ботинки stays the same.

Because it agrees with ботинки, which is plural.

In Russian, adjectives must agree with the noun in:

• gender
• number
• case

Here:

• ботинки = plural
• therefore зимние = plural too

So:

• зимний ботинок would be singular masculine
• зимние ботинки is plural

In this sentence, Сегодня most naturally sets the time for the whole situation, especially the first clause:

• Сегодня гололёд = Today it’s icy
• and because of that, я надела зимние ботинки

In practice, the listener understands that the action of putting on the boots also happened today. So сегодня effectively frames the whole sentence, even though it appears at the start of the first clause.

Yes. Russian word order is flexible, although some versions sound more natural than others depending on emphasis.

The original sentence:

• Сегодня гололёд, поэтому я надела зимние ботинки.

You could also say:

• Я надела зимние ботинки, потому что сегодня гололёд.
  = I put on winter boots because it’s icy today.

Or:

• Поэтому я надела зимние ботинки: сегодня гололёд.
  This is less neutral and more stylistically marked.

The original version is very natural because it gives the reason first, then the result.

Надела is the past tense of надеть, which is a perfective verb.

Perfective aspect is used because the sentence refers to a completed action:

• я надела зимние ботинки = I put on winter boots / I ended up wearing them

If you wanted an imperfective verb, you would usually use надевать, but that would have a different meaning, such as repeated action or process:

• Я всегда надеваю зимние ботинки, когда гололёд.
  = I always put on winter boots when it’s icy.

So надела is used here because it describes one completed act.

The stress is:

• сегóдня
• гололёд
• поэтóму
• я наделá
• зимние ботинки — usually зимние has stress on the first syllable: зИ-мние, and ботИнки on the second syllable

A rough pronunciation guide:

• сегóдня ≈ see-GOD-nya
• гололёд ≈ ga-la-LYOT
• поэтóму ≈ pa-e-TO-mu
• наделá ≈ na-de-LA
• ботИнки ≈ ba-TEEN-kee

The stress matters in Russian, so it is worth learning these words together with their stress.

Usually зимние ботинки means winter boots in the practical sense: boots meant for cold or icy weather.

It does not necessarily mean very large snow boots. It simply tells you they are the winter kind, as opposed to lighter shoes.

Depending on context, Russians might also say:

• зимние сапоги = winter boots, often taller boots
• тёплые ботинки = warm boots

So зимние ботинки is a normal and natural choice here.