Летом я отдыхаю на даче.

Летом is a very common Russian way to express time, and here it functions like an adverb meaning in summer / during the summer.

Russian often uses forms like this with seasons and parts of the day:

• зимой = in winter
• весной = in spring
• летом = in summer
• осенью = in autumn
• утром = in the morning
• вечером = in the evening

Historically, this is connected to the instrumental case, but for a learner it is often easiest to remember летом as a fixed time expression meaning in summer.

В лето is not the normal way to say in the summer in modern standard Russian.

It is the instrumental singular form of лето.

The noun is:

• nominative: лето
• instrumental: летом

In this sentence, though, it is not being used as a normal object. It is being used adverbially to express time when something happens.

So:

• Летом я отдыхаю... = In summer, I relax / spend time off...

Yes, я could be omitted.

Russian verb endings usually show who the subject is. The form отдыхаю already means I rest / I relax / I vacation, so the sentence could also be:

• Летом отдыхаю на даче.

That still means In the summer, I spend time at the dacha.

Including я makes the subject more explicit. It can sound:

• clearer
• slightly more emphatic
• more natural in some contexts, especially for beginners or when contrasting with someone else

For example:

• Летом я отдыхаю на даче, а зимой езжу в город.
  In summer I stay at the dacha, but in winter I go to the city.

Отдыхаю is the 1st person singular present tense of отдыхать.

It can mean:

• I rest
• I relax
• I am on vacation
• I spend my leisure time

In this sentence, the meaning is closer to:

• I spend the summer relaxing at the dacha
• I vacation at the dacha in summer

So it is broader than just physically resting. It often includes the idea of taking time off, relaxing, not working, or enjoying leisure time.

Russian present tense is often used for habitual or repeated actions, just like English.

So:

• Летом я отдыхаю на даче.

means something like:

• In the summer, I отдыхaю at the dacha
• more naturally: I spend summers at the dacha
• or In summer, I relax at the dacha

This is not necessarily describing what is happening right now. It can describe a regular pattern or usual behavior.

This is one of the most common questions learners ask.

Russian normally says:

• на даче = at the dacha / at the country house

Even though a dacha is a building, Russian treats it idiomatically as a place/property/setting where you stay, not just as an enclosed interior.

Compare:

• Я на даче. = I’m at the dacha.
• Я в доме на даче. = I’m in the house at the dacha.

So:

• на даче = at the dacha, at the summer place in general
• в даче would sound unnatural in most normal situations

This is something best learned as a set expression: быть / отдыхать / жить на даче.

Даче is the prepositional singular of дача.

Why? Because на can take different cases:

• на + prepositional for location: on / at
• на + accusative for motion toward something: onto / to

Here it means location, so we use the prepositional:

• дача → на даче

Compare:

• Я отдыхаю на даче. = I’m relaxing at the dacha.
• Я еду на дачу. = I’m going to the dacha.

That contrast is very important.

A дача is a very Russian cultural concept. It usually means a:

• country house
• summer house
• cottage outside the city
• place with a garden or small plot of land

For many Russians, a dacha is somewhere they go in warm weather to:

• relax
• garden
• spend weekends
• stay during holidays
• get away from the city

So на даче often suggests more than just in a house. It can imply a whole lifestyle or setting: nature, garden, fresh air, summer weekends, and so on.

Yes. Russian word order is flexible, and changing it usually affects emphasis, not the basic meaning.

All of these are possible:

• Летом я отдыхаю на даче.
• Я летом отдыхаю на даче.
• На даче я отдыхаю летом.
• Отдыхаю летом я на даче. (more marked, less neutral)

The most neutral version here is probably:

• Летом я отдыхаю на даче.

It naturally starts with the time expression летом, then gives the subject я, then the verb, then the location.

By itself, it usually sounds like a general habit or what I do in summer.

So the default understanding is:

• In summer, I stay at the dacha
• I spend summers at the dacha

If you want to make it clearly about this summer, context usually does that:

• Этим летом я отдыхаю на даче. = This summer I’m staying at the dacha.

Without extra context, the original sentence is most naturally read as habitual.

The stress is:

• ЛЕтом
• я отдыха́ю
• на ДАче

So roughly:

• LYE-tam ya at-dyh-KHA-yu na DA-che

A few notes:

• о in unstressed syllables is reduced in pronunciation
• я is pronounced like ya
• ю at the end of отдыхаю sounds like yu

A careful stress guide:

• ле́том
• отдыха́ю
• да́че