Το πρωί είχε τόσο πυκνή συννεφιά που ούτε ο ήλιος ούτε το βουνό φαίνονταν καλά.

Greek very often uses article + time word as a time expression:

• το πρωί = in the morning / this morning
• το βράδυ = in the evening / tonight
• το μεσημέρι = at noon

So Το πρωί is a normal adverbial expression. The article το is not strange here; Greek uses it much more naturally than English does in these time phrases.

Yes, είχε is literally had, but Greek often uses έχω in weather expressions.

• έχει συννεφιά = it is cloudy / there is cloud cover
• είχε συννεφιά = it was cloudy / there was cloud cover

So είχε τόσο πυκνή συννεφιά means something like there was such heavy cloud cover. Greek does not need a dummy subject like English it.

Συννεφιά is a noun meaning cloudiness, overcast weather, or cloud cover. It is feminine, so the adjective with it must also be feminine:

• πυκνή συννεφιά = dense/heavy cloud cover

Greek often prefers a noun like this where English might simply use an adjective such as cloudy.

Πυκνή is the feminine singular form of πυκνός, meaning dense, thick, or heavy. It agrees with συννεφιά, which is feminine singular.

So:

• πυκνός = masculine
• πυκνή = feminine
• πυκνό = neuter

Because συννεφιά is feminine, Greek uses πυκνή.

This is a very common Greek structure meaning so ... that.

• τόσο πυκνή συννεφιά = such dense cloud cover / cloud cover so dense
• που = that, introducing the result

So the pattern is:

• τόσο + adjective/adverb/noun phrase + που ...
• so ... that ...

Here, the cloud cover was so thick that the sun and the mountain were not clearly visible.

Ούτε ... ούτε ... means neither ... nor ....

So:

• ούτε ο ήλιος ούτε το βουνό = neither the sun nor the mountain

This is the normal Greek way to connect two negative alternatives. In this sentence, ούτε ... ούτε ... itself provides the negation, so no extra δεν is needed.

Because together they form a compound subject:

• ούτε ο ήλιος ούτε το βουνό = two things together

So the verb goes in the plural:

• φαίνονταν = were visible / could be seen

This is the same idea as in English: Neither the sun nor the mountain were visible is common in speech, though English grammar can be more variable here. In Greek, plural agreement is very natural.

Φαίνομαι can mean several related things:

• seem / appear
• be visible
• be seen

In this sentence it means be visible or could be seen:

• δεν φαινόταν = it wasn’t visible
• δεν φαίνονταν καλά = they weren’t clearly visible

So this is not about seeming in the sense of opinion; it is about actual visibility.

Greek often uses καλά after verbs to mean well, properly, distinctly, or clearly, depending on context.

With φαίνομαι, καλά means something like clearly or plainly:

• φαίνεται καλά = it is clearly visible
• δεν φαίνονται καλά = they are not clearly visible

So although καλά literally means well, the natural English translation here is clearly.

The imperfect is used because the sentence describes an ongoing situation in the past, not a single completed event.

• είχε τόσο πυκνή συννεφιά = the cloud cover was there for a period of time
• ούτε ο ήλιος ούτε το βουνό φαίνονταν καλά = during that time, they were not clearly visible

This is classic background description in Greek. English often just uses the simple past here, but Greek prefers the imperfect to show duration or ongoing state.

Greek uses the definite article much more often than English does.

• ο ήλιος = the sun
• το βουνό = the mountain

Ο ήλιος naturally takes the article, just like English the sun. Το βουνό also has the article because it refers to a specific mountain in the scene or context, not just any mountain. In Greek, using the article with concrete nouns is very common.