Learn Icelandic: Ég hata kalt veður.

Adjectives in Icelandic must match the noun they describe in gender, number, and case. The noun veður is a neuter word in the singular. Because it is the direct object of the sentence, it is in the accusative case. The neuter singular accusative form of the adjective kaldur is kalt.

Wait, if veður is in the accusative case, why doesn't its ending change?

Neuter nouns are special in Icelandic because their nominative (subject) and accusative (direct object) forms are always exactly the same. So veður looks just like its dictionary form here, even though it is grammatically in the accusative case after the verb hata.

Is hata a regular verb?

Yes, hata (to hate) is a completely regular verb belonging to the a-group. This means it keeps the -a ending in most singular forms. For example, you say ég hata (I hate), þú hatar (you hate), and hann hatar (he hates).