Kiedy pada deszcz, zakładam kalosze i idę ostrożnie przez przejście dla pieszych.

Polish usually drops subject pronouns when the verb ending already shows who is doing the action.

• zakładam = I put on / I wear
• idę = I go / I walk

So ja is not necessary. You could add ja for emphasis, but in a neutral sentence it is normally omitted.

Yes, gdy would also work.

• kiedy pada deszcz = when it rains
• gdy pada deszcz = also when it rains

In this sentence, kiedy is very natural and common in everyday speech. Gdy can sound a little more literary or formal in some contexts, but both are correct.

Because Kiedy pada deszcz is a subordinate clause: When it rains.

In Polish, a subordinate clause is normally separated by a comma from the main clause:

• Kiedy pada deszcz, zakładam kalosze...

This is more strictly required in Polish than in English.

That is simply the normal Polish expression.

Literally:

• pada = falls
• deszcz = rain

So pada deszcz is literally rain is falling, but it functions as the standard way to say it is raining / it rains.

Polish can also use other weather expressions in a similar way:

• pada śnieg = it is snowing
• wieje wiatr = the wind is blowing

Deszcz is in the nominative case.

That is because it is the grammatical subject of pada:

• deszcz pada = the rain falls

Even though English uses it in it rains, Polish does not need a dummy subject like it. The noun deszcz itself is the subject.

In Polish, the present tense is often used for habitual actions, just like in English:

• When it rains, I put on boots and walk carefully...

So zakładam here means something like I put on / I wear in a general repeated situation, not necessarily only right now.

Both verbs can be related to putting something on, but zakładać is the most natural choice for clothes, shoes, glasses, a hat, and similar items.

• zakładać kalosze = to put on rubber boots
• zakładać kurtkę = to put on a jacket
• zakładać okulary = to put on glasses

Wkładać often has more of a sense of putting into something, although in some contexts it can also refer to clothing. Here, zakładam kalosze is the normal phrasing.

Here kalosze is in the accusative plural, because it is the direct object of zakładam.

The dictionary form is the nominative plural, and for many non-masculine-personal plural nouns, the nominative and accusative plural look the same.

So:

• nominative plural: kalosze
• accusative plural: kalosze

That is why the form does not change visibly here.

This is a very common question because Polish distinguishes between two kinds of go/walk verbs.

• iść / idę = going in one direction, a specific movement
• chodzić / chodzę = going around, going habitually, repeated movement, or no single clear direction

In this sentence, idę ostrożnie przez przejście dla pieszych presents one directed action: I walk/go carefully across the pedestrian crossing. So idę is the natural choice.

If you said chodzę, it would sound more like a repeated habit of walking around in general, which does not fit as well with przez przejście dla pieszych.

Ostrożnie is an adverb, meaning carefully.

It comes from the adjective:

• ostrożny = careful

Polish often forms adverbs from adjectives in this way:

• wolny → wolno = slow / slowly
• szybki → szybko = fast / quickly
• ostrożny → ostrożnie = careful / carefully

Here it modifies the verb idę.

Przez usually means through, across, or via, depending on context.

In this sentence:

• przez przejście dla pieszych = across the pedestrian crossing / through the crosswalk area

The preposition przez requires the accusative case, which is why you get:

• przejście → accusative singular przejście

This form happens to look the same as the nominative because it is a neuter noun.

It is in the accusative singular because it follows przez.

• dictionary form: przejście (nominative singular)
• after przez: przejście (accusative singular)

For many neuter nouns in Polish, nominative and accusative singular are identical, so the form does not visibly change.

Literally, it means something like:

• przejście = crossing / passage
• dla = for
• pieszych = pedestrians

So the whole phrase is literally crossing for pedestrians, which is the normal Polish way to say pedestrian crossing or crosswalk.

Because dla requires the genitive case.

The adjective pieszy means on foot / pedestrian. In the phrase dla pieszych, it is being used like a noun meaning pedestrians.

So:

• base form: pieszy
• genitive plural: pieszych

That gives:

• przejście dla pieszych = crossing for pedestrians

Grammatically, it is an adjective form, but it is functioning like a noun.

This is very common in Polish. English does something similar in phrases like the rich, the poor, or the elderly.

So pieszych literally comes from an adjective related to being on foot, but in this phrase it means pedestrians.

Yes, Polish word order is fairly flexible, although some versions sound more natural than others.

For example, these are possible:

• Kiedy pada deszcz, zakładam kalosze i idę ostrożnie przez przejście dla pieszych.
• Zakładam kalosze i idę ostrożnie przez przejście dla pieszych, kiedy pada deszcz.

The original version is very natural because it starts with the condition: When it rains...

Polish often changes word order for emphasis, rhythm, or style, but the original sentence is a good neutral model.

Most naturally, it means a general habit:

• When it rains, I put on rubber boots and walk carefully across the crosswalk.

The present tense plus kiedy often describes what someone usually does in that situation.

If you wanted to describe one specific event in the past, you would normally use past-tense forms instead.

Sometimes, but more specifically kalosze means rubber boots, wellington boots, or rain boots.

So if you want the most accurate meaning, rubber boots or rain boots is better than just boots.