Vremea este groaznică.

Because Romanian usually puts the definite article at the end of the noun.

• vreme = weather / time, in the basic dictionary form
• vremea = the weather / the time

When talking about the weather in a general, everyday way, Romanian normally uses the definite form, so Vremea este groaznică is the natural sentence.

Este is the 3rd person singular present form of a fi, meaning to be.

So the structure is:

• vremea = the weather
• este = is
• groaznică = terrible

It works just like English is in The weather is terrible.

Yes. Very often.

In normal speech, Romanians commonly say:

• Vremea e groaznică.

This is more conversational and very natural.
Este is a little fuller and slightly more formal or careful, but both are correct.

Because Romanian adjectives agree with the noun they describe.

Here, vremea is:

• singular
• feminine

So the adjective also has to be feminine singular:

• masculine singular: groaznic
• feminine singular: groaznică

Even though groaznică comes after este, it still agrees with vremea.

The basic dictionary form is usually groaznic.

You then change it to match the noun:

• groaznic for masculine singular
• groaznică for feminine singular

Since vremea is feminine, you need groaznică.

The most neutral and standard word order is:

• Vremea este groaznică.

That is the best version for a learner to use first.

Romanian can change word order for emphasis, for example:

• E groaznică vremea.

That can sound more expressive, but the original sentence is the plain, standard version.

A rough English-friendly guide is:

VRE-mea ES-te GROAZ-ni-cuh

A few useful notes:

• vremea has two clear parts at the end: -mea
• ă in groaznică is the Romanian letter ă, a short neutral vowel, similar to the final sound in English sofa
• groaz starts with a strong gr cluster and a voiced z

You do not need a perfect English spelling approximation right away; the most important thing is recognizing ă as a separate Romanian vowel.

Yes. It is fairly strong.

Groaznică means something like:

• terrible
• awful
• horrible

So this is stronger than simply saying the weather is bad. For example:

• Vremea este rea = The weather is bad
• Vremea este groaznică = The weather is terrible

Romanian does not use a dummy subject like English it in the same way.

English often says:

• It is raining
• It is cold
• It is terrible

Romanian often uses either:

• a real noun, like vremea
• or an impersonal verb, like plouă = it is raining / it rains

So Vremea este groaznică is completely normal Romanian.

Add nu before the verb:

• Vremea nu este groaznică.
• Vremea nu e groaznică.

That means The weather is not terrible.

The easiest way is to keep the same word order and use question intonation, or a question mark in writing:

• Vremea este groaznică?
• Vremea e groaznică?

Romanian often does not need a special helping verb like English is at the beginning.

No. Vreme can also mean:

• time
• period
• era

So vremea can sometimes mean the time or the times, depending on context.

But in this sentence, with this meaning, it clearly means the weather.

Yes, in correct Romanian spelling.

The final ă is a real letter, not just decoration. It affects pronunciation and is part of the standard written form.

So the correct spelling is:

• groaznică

People may sometimes leave out diacritics online, but for learning proper Romanian, you should write them.

Usually no.

You can shorten it:

• Vremea e groaznică.

And in informal speech or writing you may also see:

• Vremea-i groaznică.

But you normally would not say:

• Vremea groaznică

That sounds incomplete in standard Romanian.

Because in Romanian, timp usually means time, not weather.

For weather, the normal word is vreme.

So:

• vremea = the weather
• timpul = the time

That is an important vocabulary distinction to remember.