A temperatura fica cada vez mais alta.

A natural breakdown is:

• A = the
• temperatura = temperature
• fica = becomes / gets
• cada vez mais = more and more
• alta = high

So a literal translation is:

• The temperature gets more and more high

But in natural English, you would usually say:

• The temperature keeps getting higher and higher
• The temperature is getting higher and higher

In Portuguese, it is very common to use the definite article (o, a, os, as) with nouns in cases where English often uses no article.

So:

• A temperatura = the temperature

Even when speaking generally, Portuguese often keeps the article:

• A temperatura está alta.
• O clima está mudando.

In English, we might say Temperature is rising in some contexts, but in Portuguese Temperatura fica cada vez mais alta without a would sound less natural in a normal sentence.

Here fica comes from the verb ficar.

Ficar can mean several things depending on context, including:

• to stay
• to remain
• to become / to get

In this sentence, it means to become / to get.

So:

• A temperatura fica alta = The temperature gets high / becomes high
• A temperatura fica cada vez mais alta = The temperature gets higher and higher

This use of ficar is very common when something changes state over time.

The difference is mainly about change versus state.

• está focuses on the current state: is
• fica focuses on becoming or getting that way: gets / becomes

Compare:

• A temperatura está alta. = The temperature is high.
• A temperatura fica cada vez mais alta. = The temperature gets higher and higher.

So fica highlights the idea that the temperature is changing.

Yes, absolutely. That is also natural Portuguese.

Both are common, but the nuance is slightly different:

• está cada vez mais alta = the temperature is increasingly high; this often sounds like an ongoing trend
• fica cada vez mais alta = the temperature gets / becomes increasingly high; this emphasizes the process of change

In many everyday situations, the two are very close in meaning.

Cada vez mais is a very common expression meaning:

• more and more
• increasingly

Literally, cada vez is something like each time, so the whole phrase gives the idea of something increasing over time.

Examples:

• cada vez mais difícil = more and more difficult
• cada vez mais rápido = faster and faster / more and more quickly
• cada vez mais caro = more and more expensive

It is an extremely useful pattern in Portuguese.

Because alta has to agree with temperatura.

In Portuguese, adjectives usually agree in gender and number with the noun they describe.

• temperatura is feminine singular
• so the adjective must also be feminine singular: alta

Compare:

• A temperatura está alta.
• O preço está alto.

Here:

• temperatura → feminine → alta
• preço → masculine → alto

Because with temperatura, Portuguese normally uses alta and baixa, not quente and fria.

So:

• temperatura alta = high temperature
• temperatura baixa = low temperature

This works a lot like English, where we usually say:

• high temperature
• low temperature

rather than hot temperature.

You can say:

• Está quente. = It’s hot.
• A temperatura está alta. = The temperature is high.

Both can refer to heat, but they are used differently.

Because this is not a direct comparison with another specific thing. It is a progressive increase.

• cada vez mais alta already means higher and higher / more and more high

You use do que when you compare one thing directly to another:

• A temperatura está mais alta do que ontem.
  = The temperature is higher than yesterday's

But in:

• A temperatura fica cada vez mais alta

the comparison is implicit: it is higher than it was before.

Fica is the third-person singular present indicative of ficar.

That means it matches a temperatura, which is singular:

• eu fico
• você/ele/ela fica
• a temperatura fica

The present tense in Portuguese is often used for:

• things happening now
• regular patterns
• general truths
• trends

So here it works well for an ongoing tendency: the temperature keeps rising.

A simple English-friendly approximation is:

ah tem-peh-rah-TOO-rah FEE-kah KAH-dah vez myz AHL-tah

A few pronunciation notes:

• temperatura has the stress on tu: tem-pe-ra-TU-ra
• fica sounds like FEE-kah
• mais sounds like mys or myz
• alta sounds roughly like AHL-tah

In natural speech, words can link together a bit, especially vez mais.

It can be understood either way, depending on context.

Most commonly, it means:

• the temperature in this situation
• or temperature as a general phenomenon being discussed

For example, it could refer to:

• the weather during the day
• global warming
• the temperature in a room, machine, or experiment

Portuguese often uses the definite article in these cases, so a temperatura does not always mean one very narrowly defined temperature. Context tells you how specific it is.