Сегодня на улице пасмурно, поэтому мне хочется пить горячий чай.

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

So:

• Сегодня на улице пасмурно = Today it is gloomy outside
• Literally, it is more like Today outside gloomy

This is completely normal in Russian.
Compare:

• Он студент. = He is a student
• Мама дома. = Mom is at home

But in the past or future, forms of быть appear:

• Вчера было пасмурно. = Yesterday it was gloomy
• Завтра будет пасмурно. = Tomorrow it will be gloomy

Yes, literally на улице means on the street, but very often in Russian it is used idiomatically to mean outside / outdoors.

So:

• на улице холодно = it’s cold outside
• на улице дождь = it’s raining outside / there’s rain outside

This is one of the most common ways to talk about weather in everyday Russian.

Grammatically:

• улица = street
• на улице = on the street / outside
  Here улице is prepositional case after на when talking about location.

Because пасмурно is being used as a predicative adverb/state word, not as an adjective describing a noun.

In this sentence, Russian is not saying:

• the day is gloomy
• the weather is gloomy

Instead, it says something more like:

• outside is gloomy
• it is gloomy outside

So Russian uses пасмурно, not an adjective that must agree with a noun.

Compare:

• Сегодня пасмурно. = It’s gloomy today.
• Погода пасмурная. = The weather is gloomy.

In the second sentence, пасмурная is an adjective agreeing with погода.

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

It connects the two ideas:

• Сегодня на улице пасмурно = one situation
• поэтому мне хочется пить горячий чай = the result

So the logic is:

It’s gloomy outside today, therefore I feel like drinking hot tea.

A small pronunciation note:

• по́этому — stress is on the first syllable

Also, the comma before поэтому is standard here because it joins two clauses.

Because хочется does not work like a normal verb with a nominative subject such as я.

In this pattern, the person who experiences the feeling is put in the dative case:

• мне хочется = I feel like...
• тебе хочется = you feel like...
• ему хочется = he feels like...

So:

• мне = dative form of я
• literally: to me it is wanted or to me there is a desire

This is a very Russian way to express a feeling or urge.

Compare:

• Я хочу пить чай. = I want to drink tea.
• Мне хочется пить чай. = I feel like drinking tea.

The second one sounds softer, more like a spontaneous desire.

This is a very common learner question.

хочу

This is the normal 1st person singular form of хотеть:

• Я хочу чай. = I want tea.
• Я хочу пить чай. = I want to drink tea.

It sounds direct and straightforward.

хочется

This is a different, more impersonal-feeling construction:

• Мне хочется чая.
• Мне хочется пить чай.

It often means:

• I feel like...
• I have a craving / urge to...
• I’m in the mood for...

So in this sentence, мне хочется пить горячий чай is more natural than я хочу пить горячий чай if the speaker means a mood or feeling caused by the weather.

Because Russian often uses хочется + infinitive to say feel like doing something.

So:

• мне хочется спать = I feel like sleeping / I’m sleepy
• мне хочется есть = I feel like eating / I’m hungry
• мне хочется пить горячий чай = I feel like drinking hot tea

The infinitive names the action that the speaker feels like doing.

Structure:

• мне = to me
• хочется = is desired / I feel like
• пить = to drink
• горячий чай = hot tea

Because in this sentence чай is the direct object of пить, so it is in the accusative case.

For an inanimate masculine noun like чай, the accusative singular looks the same as the nominative singular:

• nominative: горячий чай
• accusative: горячий чай

So even though the form does not change, the function is accusative here.

Why not горячего чая?

That form is genitive, and it can appear in some other patterns, for example:

• Мне хочется горячего чая. = I feel like some hot tea.

That version is also correct, but the structure is different:

• мне хочется пить горячий чай = I feel like drinking hot tea
• мне хочется горячего чая = I feel like having some hot tea

Both are natural, but the original sentence focuses on the action пить.

Russian treats чай as a normal noun, and singular is perfectly natural here.

• пить чай = to drink tea
• горячий чай = hot tea

This is like talking about tea as a drink in general, not about multiple separate teas.

If you wanted to talk about different kinds or servings in some contexts, plural could appear, but singular is the standard choice here.

Yes. Russian word order is flexible, although the original sentence is very natural.

Original:

• Сегодня на улице пасмурно, поэтому мне хочется пить горячий чай.

Possible variations:

• На улице сегодня пасмурно, поэтому мне хочется пить горячий чай.
• Мне хочется пить горячий чай, потому что сегодня на улице пасмурно.

These all make sense, but the emphasis changes slightly.

The original order is good because it first gives the setting:

1. Today
2. outside
3. it’s gloomy
4. therefore
5. I feel like drinking hot tea

That progression sounds smooth and natural.

Sometimes yes, but not as a direct replacement in the same structure.

• поэтому = therefore / so / that’s why
• из-за этого = because of this

Your sentence with поэтому is clean and natural:

• Сегодня на улице пасмурно, поэтому мне хочется пить горячий чай.

If you use из-за этого, the wording usually changes a bit:

• Сегодня на улице пасмурно, и из-за этого мне хочется пить горячий чай.

That means:

• Today it’s gloomy outside, and because of this I feel like drinking hot tea.

This is understandable, but поэтому is simpler and more idiomatic here.

Mostly it refers to overcast, gloomy, cloudy weather.

It does not necessarily mean that it is raining. It suggests:

• gray sky
• little sun
• dull weather

So пасмурно is often best translated as:

• overcast
• gloomy
• cloudy
  depending on context

It can also create a certain atmosphere or mood in the sentence, which is why it fits well with wanting горячий чай.

Then the logic would be reversed.

Original:

• Сегодня на улице пасмурно, поэтому мне хочется пить горячий чай.
• It’s gloomy outside today, so I feel like drinking hot tea.

With потому что:

• Мне хочется пить горячий чай, потому что сегодня на улице пасмурно.
• I feel like drinking hot tea because it’s gloomy outside today.

So:

• поэтому introduces the result
• потому что introduces the cause

Both are correct; they just organize the sentence differently.