На дачу я беру шорты, сандалии и кепку, потому что там жарко с утра.

With дача, Russian normally uses на for going there, being there, and coming back from there:

• на дачу = to the dacha
• на даче = at the dacha
• с дачи = from the dacha

This is just the standard idiomatic pattern. Not every place in Russian uses в. For example, you say в город but на дачу.

Because на here shows movement toward a destination, it takes the accusative case.

So:

• на дачу = to the dacha
• на даче = at the dacha

This is a very common contrast in Russian:

• куда? → accusative: на дачу
• где? → prepositional: на даче

Russian word order is much more flexible than English word order. Starting with На дачу puts the destination first and gives it a little emphasis, like:

As for the dacha, I’m taking...

A more neutral order would be:

• Я беру шорты, сандалии и кепку на дачу.
• Я беру на дачу шорты, сандалии и кепку.

All of these are possible. The version in your sentence sounds natural and slightly highlights where the things are being taken.

Yes, it could be omitted.

Russian often leaves out subject pronouns when the verb already makes the subject clear:

• На дачу беру шорты, сандалии и кепку.

That is still grammatical. Including я adds a bit of emphasis or clarity. It can sound like the speaker is specifically talking about what I am taking.

In Russian, the present tense can often correspond to English I take, I’m taking, or sometimes even a planned near-future action, depending on context.

So я беру here can mean:

• I take
• I’m taking

If the speaker wanted to emphasize a single completed future action, Russian might use the perfective verb возьму:

• На дачу я возьму шорты... = I’ll take shorts to the dacha...

But беру sounds very natural if the speaker is talking about what they usually take, or what they are taking in the current situation.

These are the direct objects of беру, so they are in the accusative case.

Why the forms look different:

• шорты stays шорты
• сандалии stays сандалии
• кепка becomes кепку

That happens because:

1. Кепка is a singular feminine noun ending in -а, so in the accusative singular it changes to -у.
2. Шорты and сандалии are plural inanimate nouns, and for inanimate plurals, the accusative usually looks the same as the nominative.

So the whole list is accusative, even though not every word visibly changes.

Жарко is used in impersonal sentences about temperature or general conditions:

• Здесь жарко. = It’s hot here.
• Там жарко. = It’s hot there.

This is different from жаркий, which is an adjective and must describe a noun:

• жаркий день = a hot day
• жаркая погода = hot weather

So in там жарко, Russian is not describing a noun. It is simply stating a condition: it’s hot there.

С утра is an idiomatic expression meaning something like:

• from early morning
• since the morning began
• already in the morning

In this sentence, it suggests that the heat starts early and continues:

it’s hot there from the morning onward

It is a little stronger than simply saying утром (in the morning), because с утра often gives the idea that something is true starting early in the day.

Because Russian often avoids repeating the same noun or phrase when it is already clear.

So:

• потому что там жарко с утра

  means:

• because it’s hot there from early morning

Here там clearly refers back to на дачу. You could also say:

• потому что на даче жарко с утра

But там sounds smoother and less repetitive.

Because потому что introduces a subordinate clause, and in Russian that clause is normally separated by a comma.

So the structure is:

• main clause: На дачу я беру шорты, сандалии и кепку
• subordinate clause: потому что там жарко с утра

That is why the comma is required:

..., потому что там жарко с утра.