Learn Hardcore Icelandic: Veðrið er hvorki heitt né kalt í dag. - The weather is neither hot nor cold today.

It’s the Icelandic equivalent of English neither … nor. Put hvorki before the first item you’re negating and né before the second (and any further) item.

With adjectives: Veðrið er hvorki heitt né kalt. = The weather is neither hot nor cold.
With nouns: Ég á hvorki bíl né hjól. = I have neither a car nor a bike.
With verbs: Ég hvorki borða né drekk. = I neither eat nor drink.

Why are the adjectives heitt and kalt in the form ending with -t?

Because they agree with the grammatical gender and number of the subject veðrið, which is neuter singular. Predicative adjectives (after vera “to be”) take the strong declension and match the subject:

heitur (m), heit (f), heitt (n)
kaldur (m), köld (f), kalt (n) So with neuter veðrið, you use heitt and kalt.

Why is it veðrið (definite “the weather”) and not just veður?

Icelandic normally talks about the current weather as a definite, known thing, so veðrið (“the weather”) is standard in statements like this. The base noun is veður (neuter); the definite singular is veðrið. Saying bare Veður er … here would sound odd in everyday speech.

Where can I put í dag in the sentence? Is the word order flexible?

Yes. Common options:

Neutral: Veðrið er hvorki heitt né kalt í dag.
Fronted time for emphasis (verb-second rule): Í dag er veðrið hvorki heitt né kalt.
Middle position is possible but less common: Veðrið er í dag hvorki heitt né kalt. Remember Icelandic main clauses are verb-second, so if you front Í dag, the verb er must be the second element.

Can I add ekki somewhere, like “Veðrið er ekki hvorki heitt né kalt”?

No. Hvorki already carries the negation, so don’t add ekki to the same clause: Veðrið er hvorki heitt né kalt is correct.

If you don’t use hvorki, you can have a pattern with ekki … né …: Veðrið er ekki heitt né kalt. (not hot nor cold). But don’t combine ekki with hvorki.

Can I list more than two items with hvorki … né?

Yes. You can chain né:

Ég borða hvorki kjöt né fisk né egg. = I eat neither meat nor fish nor eggs.

Is hvorki … né only for adjectives? Can I use it with verbs or nouns too?

You can use it across categories:

Verbs: Ég hvorki sef né borða eftir miðnætti.
Nouns/objects: Hún á hvorki bíl né reiðhjól.
Adjectives (your sentence): Veðrið er hvorki heitt né kalt.

How do I pronounce the sentence? Any tips for ð, hv, tt, and é?

Approximate pronunciations:

Veðrið ≈ “VEH-thrith” (voiced English “th” as in “this” for ð)
er ≈ “air”
hvorki ≈ “KWOR-ki” (modern Icelandic hv is typically like “kv”)
heitt ≈ “HATE-ht” (the tt is pre-aspirated; you hear a light “h” before t)
né ≈ “nyeh” (é sounds like “yeh”; with n it comes out “nyeh”)
kalt ≈ “kal-t”
í dag ≈ “ee dahg” Tips:
ð is a voiced “th” (as in “this”), unlike þ, which is voiceless (as in “thin”).
hv is pronounced like “kv” for most speakers.
Double tt often has that little breathy “h” before the t (pre-aspiration).
é is roughly “yeh.”

What case is dag in í dag, and why?

It’s accusative. The preposition í can govern different cases, but in time expressions like í dag (“today”), í takes the accusative. The noun is dagur (day): nominative dagur, accusative dag.

What’s the Icelandic for “either … or,” the opposite of neither … nor?

Use annaðhvort … eða:

Veðrið er annaðhvort heitt eða kalt í dag. = The weather is either hot or cold today.

What are the base dictionary forms behind heitt and kalt?

heitt comes from the adjective heitur (m), heit (f), heitt (n) = hot.
kalt comes from kaldur (m), köld (f), kalt (n) = cold. In your sentence they’re neuter singular strong forms agreeing with veðrið.

Could I use milder words like “warm” or “cool” instead of “hot/cold”?

Yes:

hlýtt = warm (from hlýr/hlý)
svalt = cool (from svalur/svöl/svalt) Example: Veðrið er hvorki hlýtt né svalt í dag.

How would I turn the statement into a yes/no question?

Keep verb-second order and raise the intonation:

Er veðrið hvorki heitt né kalt í dag? = Is the weather neither hot nor cold today?