Learn Hardcore German: Ich stelle fest, dass die Temperatur im Haus hoch ist. - I realize that the temperature in the house is high.

Ich stelle fest literally translates to “I establish firmly,” but in everyday use it means “I notice,” “I observe,” or “I ascertain.” It’s the first-person singular present of the separable verb feststellen.

Why is there a dass clause after stelle fest?

The verb feststellen commonly takes a dass-clause as its object to specify what is being noticed or confirmed—just like English “I notice that ….” In German, such subordinate clauses are introduced by dass, and they send the finite verb to the end.

Why is the verb ist at the very end of the subordinate clause?

Because in German subordinate clauses (those introduced by dass or similar conjunctions), the conjugated verb goes to the final position. The pattern is:

conjunction (dass)
subject and other elements
finite verb (ist)

Why is it im Haus and not ins Haus?

im = in dem, indicating a static location (“in the house”)
ins = in das, indicating motion into (“into the house”)
Since you’re talking about the temperature inside (a location), you must use im Haus.

Why is Temperatur feminine and why is die Temperatur in the nominative case?

Gender: In German each noun has one of three genders. Temperatur is feminine, so its definite article is die.
Case: In dass die Temperatur … ist, die Temperatur is the subject of the subordinate clause, so it takes the nominative case. The feminine nominative singular article is die.

Why does hoch appear after the verb and not before Temperatur?

Here hoch is used as a predicative adjective (linked by the verb ist). Predicative adjectives in German follow the verb without any ending. If you wanted an attributive adjective before the noun, you’d write die hohe Temperatur, with the adjective carrying the proper ending for gender, number, and case.

Why is stelle fest split apart in the main clause?

Feststellen is a separable-prefix verb. In a main clause, the prefix fest detaches and moves to the end of the clause, while the finite verb stelle occupies the second position: Ich stelle fest.

Can you replace feststellen with merken or bemerken? What’s the difference?

merken: often “to notice” (sensory or sudden awareness) or “to remember.”
bemerken: “to notice” or “to remark,” with a nuance of verbal comment.
feststellen: implies a deliberate observation or conclusion, often based on evidence or measurement.
So while bemerken could work, feststellen conveys a more formal, fact-finding tone.

Could I rephrase the sentence using a colon instead of a dass clause?

Yes. A common alternative is:
Ich stelle fest: Die Temperatur im Haus ist hoch.
This structure (main clause + colon + independent clause) can feel more direct or emphatic in both speech and writing.

Why is Temperatur capitalized in German?

In German, all nouns are capitalized no matter where they appear in a sentence. That’s why Temperatur, like every other noun, begins with a capital letter.