Wilgotność jest wysoka.

In a normal present-tense sentence like this, Polish usually does use jest:

• Wilgotność jest wysoka. = The humidity is high.

Unlike some other Slavic languages, standard Polish normally keeps the present-tense form of być (to be) in ordinary statements.

You may sometimes see it omitted in:

• headlines
• notes
• very informal, clipped style

For example, Wilgotność wysoka might appear on a display, chart, or weather readout, but in full standard speech, jest is the normal choice.

Because the adjective has to agree with the noun it describes.

Wilgotność is:

• feminine
• singular

So the adjective must also be:

• feminine
• singular

That gives:

• masculine: wysoki
• feminine: wysoka
• neuter: wysokie

So:

• wysoka temperatura
• wysoka wilgotność

but:

• wysoki poziom
• wysokie ciśnienie

It is in the nominative case.

In this sentence:

• wilgotność is the subject
• jest wysoka is the predicate

So Polish uses the nominative for the subject:

• Wilgotność jest wysoka.

The adjective wysoka is also nominative here, agreeing with the subject after jest.

Wilgotność is a feminine noun.

A very useful clue is the ending -ość. Nouns ending in -ość are typically feminine abstract nouns, often like English nouns ending in -ness, -ity, or -tion.

Examples:

• wilgotność = humidity
• wysokość = height
• jakość = quality
• możliwość = possibility

So once you recognize -ość, it becomes easier to predict adjective agreement:

• wilgotność jest wysoka
• jakość jest dobra

A rough guide:

• wilgotność ≈ veel-GOTNoshch
• jest ≈ yest
• wysoka ≈ vih-SO-ka

A few useful details:

• Polish stress is usually on the second-to-last syllable:

  • wilGOTność
  • wySOka
• w sounds like English v
• j sounds like English y
• y is a Polish vowel that does not sound exactly like English ee or ih; it is a distinct Polish sound
• the ending -ść is a soft cluster, somewhat like a soft sh/ch combination

You do not need a perfect English approximation right away; the most important thing is to hear it from native audio and imitate the rhythm.

Yes. Wysoka wilgotność and wilgotność jest wysoka are both very natural and common.

Polish often uses high/low with measurements, levels, and weather-related values, just like English:

• wysoka wilgotność = high humidity
• niska wilgotność = low humidity
• wysoka temperatura = high temperature
• wysokie ciśnienie = high pressure

You might also hear expressions with duża in some contexts, but wysoka wilgotność is the standard, natural collocation.

Yes, Polish word order is more flexible than English, but the basic order here is the most neutral:

• Wilgotność jest wysoka.

Other orders are possible, but they change the emphasis:

• Wysoka jest wilgotność.
  This sounds marked or contrastive, as if emphasizing high.

• Jest wysoka wilgotność.
  This can occur in some contexts, but it is less neutral and often feels more like There is high humidity.

For a learner, the safest default is:

• subject + jest + adjective

No, that would not be correct here.

Polish to can link two nouns or noun phrases:

• To jest problem.
• Wilgotność to problem.

But with an adjective like wysoka, you normally use jest:

• Wilgotność jest wysoka.

So:

• noun + jest + adjective ✅
• noun + to + adjective ❌

You put nie before jest:

• Wilgotność nie jest wysoka. = The humidity is not high.

This is the normal pattern in Polish:

• Temperatura jest niska.
• Temperatura nie jest niska.

With być, the negative particle nie is written separately:

• nie jest
• nie była
• nie będzie

In speech, Polish often makes a yes/no question mainly through intonation:

• Wilgotność jest wysoka? = Is the humidity high?

You can also use czy at the beginning, which is very common and clear:

• Czy wilgotność jest wysoka?

For learners, czy + sentence is an excellent pattern to use.

Normally, wilgotność is an uncountable abstract noun, like humidity in English.

So you usually say:

• Wilgotność jest wysoka.
• Wilgotność powietrza jest wysoka. = The air humidity is high.

You would not normally use it like one humidity, two humidities.

If you need to be more specific, Polish often adds another noun:

• wilgotność powietrza = air humidity
• poziom wilgotności = humidity level

They are related, but not identical.

• wilgotność = humidity, moisture level, often used in measurements, weather, science, and technical contexts
• wilgoć = dampness, moisture, often referring more to actual moisture or damp conditions

So in a sentence like this, wilgotność jest wysoka is the natural choice for humidity is high.

Examples:

• Wilgotność powietrza jest wysoka. = The air humidity is high.
• W domu jest wilgoć. = There is dampness/moisture in the house.

It is understandable, but wysoka is more natural.

Polish often uses wysoki/niski with:

• levels
• rates
• values
• pressure
• temperature
• humidity

So:

• Wilgotność jest wysoka. ✅ natural
• Wilgotność jest duża. understandable, but less idiomatic in this context

A good habit is to learn these common adjective-noun pairings as chunks:

• wysoka wilgotność
• niska temperatura
• wysokie ciśnienie