W sierpniu biegam rano, bo po południu jest za gorąco.

Because after w when talking about a time period like a month, Polish uses the locative case.

• sierpień = August
• w sierpniu = in August

This is a very common pattern:

• w styczniu = in January
• w maju = in May
• w listopadzie = in November

So w sierpniu means in August.

Both come from verbs meaning to run, but they are used differently.

• biegam comes from biegać and usually means I run regularly / habitually
• biegnę comes from biec and usually means I am running / I run right now in one specific instance

In this sentence, the speaker means something like In August, I run in the morning as a habit or routine, so biegam is the natural choice.

Compare:

• Codziennie biegam rano. = I run every morning.
• Teraz biegnę do sklepu. = I’m running to the shop now.

Polish often drops subject pronouns when they are clear from the verb ending.

• biegam already means I run
• the ending -am tells you it is 1st person singular

So:

• Biegam rano = I run in the morning
• Ja biegam rano = I run in the morning

Adding ja is possible, but it usually adds emphasis, contrast, or emotion.

Rano means in the morning or simply in the morning time.

It is an adverb, so it does not change its form.

Examples:

• Wstaję rano. = I get up in the morning / early
• Biegam rano. = I run in the morning

Depending on context, rano can sometimes also suggest early in the day, but here the main meaning is just in the morning.

Bo means because.

It is very common in everyday spoken and written Polish. In this sentence:

• bo po południu jest za gorąco = because in the afternoon it is too hot

Yes, you can often use ponieważ instead. It is a bit more formal or neutral.

Compare:

• Biegam rano, bo po południu jest za gorąco.
• Biegam rano, ponieważ po południu jest za gorąco.

Both are correct. Bo sounds more natural in casual conversation.

Po południu is a fixed expression meaning in the afternoon.

Literally, it comes from after noon, but in modern Polish it simply functions as the normal way to say in the afternoon.

Grammatically:

• po often requires the locative case
• południe becomes południu

So:

• południe = noon
• po południu = in the afternoon / after noon

This expression is extremely common and best learned as a whole chunk.

Because za means too, not just very.

• bardzo gorąco = very hot
• za gorąco = too hot

So the sentence means that the afternoon is excessively hot, hot enough to be a problem for running.

More examples:

• Jest za zimno. = It’s too cold.
• Jest bardzo zimno. = It’s very cold.

That difference is important.

Because gorąco is the form used in weather or general-condition expressions like it is hot.

• gorący is an adjective meaning hot and is used with a noun:

  • gorąca kawa = hot coffee
  • gorący dzień = a hot day

• gorąco is used more like hot in It’s hot:

  • Jest gorąco. = It’s hot.

So in jest za gorąco, Polish uses the adverb-like/predicative form gorąco, not the adjective gorący.

Yes, Polish word order is more flexible than English, although some orders sound more natural than others.

The original sentence:

• W sierpniu biegam rano, bo po południu jest za gorąco.

is natural and clear.

You could also hear things like:

• Rano biegam w sierpniu, bo po południu jest za gorąco.
• Biegam rano w sierpniu, bo po południu jest za gorąco.

But changing the order can slightly change what is emphasized.

The original version puts w sierpniu first, so it highlights the time frame in August.

By itself, w sierpniu usually means in August and can be understood from context in different ways.

It might mean:

• this August
• in August in general
• every August as a repeated seasonal habit

Because the verb biegam suggests a habitual action, many learners will naturally hear it as something like:

• In August, I run in the morning, because in the afternoon it’s too hot

So it often sounds like a general pattern for that month, unless the wider context makes it clearly about one specific August.

A few sounds here are often tricky for English speakers:

• si before a vowel sounds like a soft sh/sy sound
• ń is a soft ny sound
• ł sounds like English w
• ą is a nasal vowel, often sounding somewhat like on/om depending on context
• ci before a vowel is a soft ch/t-like sound

Rough guides:

• sierpniu ≈ SHERP-nyu
• południu ≈ po-WOOD-nyu
• gorąco ≈ go-RON-tso

These are only approximations, but they can help at first.

Yes, it sounds natural.

It has a very typical Polish structure:

• time phrase first: W sierpniu
• main action: biegam rano
• reason clause with bo: bo po południu jest za gorąco

It is exactly the kind of sentence a native speaker could say in everyday conversation.