Pogoda jest okropna.

• pogoda = weather
• jest = is
• okropna = awful / terrible / horrible

So the structure is:

subject + verb + adjective

That is very similar to English: The weather is awful.

The dictionary form is być, which means to be.

Jest is the 3rd person singular present form, so it means is.

A few related forms are:

• jestem = I am
• jesteś = you are
• jest = he/she/it is
• jesteśmy = we are
• jesteście = you are
• są = they are

Because okropna has to agree with pogoda.

In Polish, adjectives change form to match the noun’s:

• gender
• number
• case

Pogoda is:

• feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• masculine: okropny
• feminine: okropna
• neuter: okropne

That is why Pogoda jest okropna is correct.

A very common clue is the ending -a.

Most Polish nouns ending in -a are feminine, and pogoda is one of them.

Because it is feminine, other words connected to it often take feminine forms too, such as:

• ta pogoda = this weather
• ładna pogoda = nice weather
• okropna pogoda = awful weather

Both are in the nominative here.

• pogoda is nominative because it is the subject of the sentence.
• okropna is also nominative because it is a predicate adjective used with być.

This is useful because English speakers sometimes expect a different case after to be. In Polish:

• with an adjective, you normally use the nominative
  
  • Pogoda jest okropna
• with a noun, Polish often uses the instrumental
  
  • Ona jest nauczycielką = She is a teacher

So in this sentence, okropna is nominative, not instrumental.

Because Polish does not have articles like a / an / the.

So pogoda can mean:

• weather
• the weather

The exact meaning depends on context. In a sentence like this, English usually translates it as the weather.

In normal standard Polish, you should keep jest:

Pogoda jest okropna.

Sometimes native speakers omit it in very informal, shortened, or expressive speech:

Pogoda okropna.

That sounds more like:

• a note
• a headline
• a casual comment
• an emotional shorthand

For learners, the safest choice is to use jest.

A rough English-style guide is:

po-GO-da yest o-KROP-na

A few pronunciation tips:

• j sounds like English y in yes
• g is always a hard g, like in go
• o is a clear short o
• stress usually falls on the second-to-last syllable

So:

• pogoda → stress on GO
• okropna → stress on KROP

Yes, but Pogoda jest okropna is the most neutral and natural order.

Other orders are possible, but they sound more marked:

• Okropna jest pogoda. = more emphasis on awful
• Jest okropna pogoda. = possible in some contexts, but less neutral

For most learners, the default pattern is best:

subject + jest + adjective

Yes. Okropna is fairly strong and usually means something like:

• awful
• terrible
• horrible

If you want something milder, Polish often uses:

• brzydka pogoda = bad / nasty weather, literally ugly weather
• fatalna pogoda = terrible weather
• nieprzyjemna pogoda = unpleasant weather

So Pogoda jest okropna sounds stronger than just The weather is bad.

Yes, but that is a slightly different structure.

• okropna pogoda = awful weather
• Pogoda jest okropna = The weather is awful

In okropna pogoda, the adjective comes directly before the noun.

In Pogoda jest okropna, the adjective comes after jest because it is describing the subject through the verb to be.

You just change the form of być:

• Pogoda była okropna. = The weather was awful.
• Pogoda będzie okropna. = The weather will be awful.

The adjective okropna stays feminine singular because it still agrees with pogoda.