Hádegissólin er of heit í dag.

It is a compound word:

• hádegi = noon
• sól = sun
• -in = the definite article suffix, meaning the

So hádegissólin means literally the noon-sun or the midday sun.

Icelandic makes compounds very freely, much more than English does, so a learner will often see long words like this.

The double ss comes from how the compound is built.

The first part, hádegi, often appears in compounds as hádegis-. Then you add sól:

• hádegis
  • sól → hádegissól

So one s comes from the first element and one from sól itself.

This kind of linking consonant is very common in Icelandic compounds.

Because Icelandic usually puts the at the end of the noun instead of using a separate word.

Compare:

• sól = sun
• sólin = the sun

The same thing happens with the whole compound:

• hádegissól = midday sun
• hádegissólin = the midday sun

So the definite article is attached as a suffix.

No. Icelandic nouns are not normally capitalized.

It is capitalized here only because it is the first word in the sentence.

So in the middle of a sentence, you would normally write hádegissólin, not Hádegissólin.

Because the adjective has to agree with hádegissólin, which is feminine singular.

The adjective heitur = hot has different forms:

• heitur = masculine
• heit = feminine
• heitt = neuter

Since sól is feminine, you get:

• Hádegissólin er of heit.

This is adjective agreement, and it is very important in Icelandic.

No. Icelandic of here means too or overly.

So:

• of heit = too hot

It is not related to the English preposition of.

A useful comparison:

• mjög heit = very hot
• of heit = too hot

So of usually suggests excess.

Er is the present singular form of vera, which means to be.

So:

• vera = to be
• er = is

In this sentence:

• Hádegissólin er of heit í dag.
• The midday sun is too hot today.

Since the subject is singular, er is the correct form.

Because Icelandic often uses a prepositional phrase where English uses a single adverb.

• í = in
• dag = day (here in the correct case after the preposition)

So í dag literally means in day, but idiomatically it means today.

This is a very common everyday expression.

Yes. That is also correct.

Icelandic often allows different word order depending on what you want to emphasize. If you put Í dag first, you are foregrounding today.

So both of these work:

• Hádegissólin er of heit í dag.
• Í dag er hádegissólin of heit.

But when something other than the subject comes first, Icelandic normally keeps the finite verb in second position. That is why you get Í dag er..., not Í dag hádegissólin er...

A rough guide is:

• Hádegissólin ≈ HOW-they-yis-so-lin
• er ≈ ehr
• of ≈ ov
• heit ≈ hayt
• í dag ≈ ee dahg

A few useful pronunciation notes:

• á is roughly like ow in now
• ó is roughly like o in go
• ei in heit sounds like ay
• stress usually falls on the first syllable of Icelandic words

English-style approximations are never perfect, but they can help you get started.