Όταν βρέχομαι και κάνει πολύ κρύο, παθαίνω εύκολα συνάχι.

Yes, βρέχομαι is formally a mediopassive verb form, but in Modern Greek it often has an active-like meaning: I get wet.

So:

• βρέχω = I wet something
• βρέχομαι = I get wet / I am getting wet

In this sentence, Όταν βρέχομαι means When I get wet.

This is very common in Greek: some mediopassive forms are not best translated with an English passive, but with a natural English intransitive expression.

Κάνει κρύο is the standard Greek way to say it is cold in the sense of the weather is cold.

Literally, κάνει means it makes / it does, but as a weather expression it simply means:

• κάνει κρύο = it is cold
• κάνει ζέστη = it is hot
• κάνει καλό καιρό = the weather is good

You can sometimes use είναι κρύο, but that usually describes something as being cold:

• Το νερό είναι κρύο = The water is cold
• Έξω κάνει κρύο = It is cold outside

So in this sentence, κάνει πολύ κρύο is exactly the natural weather expression.

Because the sentence is talking about a general repeated situation, not one single event.

Όταν + present tense often means whenever or when(ever) in general statements:

• Όταν βρέχομαι... = When/Whenever I get wet...
• Όταν κάνει κρύο... = When/Whenever it is cold...

Greek often uses the present tense for habits and repeated truths where English may also use the present:

• When I get wet and it’s very cold, I easily catch a cold.

So the present tense here does not mean only right now. It can also describe what usually happens.

Παθαίνω is a very common Greek verb meaning something like:

• to suffer
• to get
• to come down with
• to be affected by

In this sentence, παθαίνω συνάχι means I get a cold / I come down with a cold.

It is not a word-for-word match with English. Greek often uses παθαίνω with illnesses or unpleasant conditions:

• παθαίνω γρίπη = I get the flu
• παθαίνω ζημιά = I suffer damage
• τι έπαθες; = what happened to you? / what’s wrong?

So here it is a very natural choice.

Συνάχι usually refers to a cold, especially with the idea of a runny or blocked nose.

Depending on context, it can be understood as:

• a cold
• a head cold
• nasal congestion / sniffles

So in this sentence, the natural English meaning is I easily catch a cold.

A learner should note that Greek illness words do not always map perfectly onto English words, but συνάχι here is close enough to a cold.

Because Greek often omits the article with illnesses or conditions in expressions like this.

So:

• παθαίνω συνάχι = I get a cold
• έχω πυρετό = I have a fever
• έχω πονοκέφαλο = I have a headache

English uses a in a cold, but Greek does not need an indefinite article here.

That is very normal and idiomatic.

Εύκολα means easily.

It modifies the verb phrase παθαίνω συνάχι, so the idea is:

• παθαίνω εύκολα συνάχι = I easily get a cold
• more natural English: I catch a cold easily

It tells you that this happens readily / without much resistance / quite often under those conditions.

Its position is flexible in Greek. You could also hear:

• εύκολα παθαίνω συνάχι
• παθαίνω συνάχι εύκολα

But the original order is perfectly natural.

In Greek, subject pronouns are often omitted because the verb ending already shows the person and number.

Here:

• βρέχομαι = I get wet
• παθαίνω = I get / I suffer

Both verb forms clearly indicate first person singular, so Greek does not need εγώ.

You would only add εγώ if you wanted emphasis or contrast:

• Εγώ παθαίνω εύκολα συνάχι, αλλά ο αδερφός μου όχι.
• I catch a cold easily, but my brother doesn’t.

Here και means and, linking the two conditions:

• Όταν βρέχομαι = when I get wet
• και κάνει πολύ κρύο = and it is very cold

Together, they describe the situation in which the result happens.

In natural English, you might translate it as:

• When I get wet and it’s very cold, I easily catch a cold.

So there is nothing especially unusual about και here.

It describes a general tendency / habitual situation.

The present tense throughout suggests:

• Whenever this happens, this is the result
• not this is happening right now

So the sentence means something like:

• When I get wet and it’s very cold, I tend to catch a cold easily.

That habitual meaning is very common with όταν + present.

Yes, but it would change the structure and slightly shift the meaning.

Κρυώνω means I am cold / I feel cold.

So you could say something like:

• Όταν βρέχομαι και κρυώνω πολύ, παθαίνω εύκολα συνάχι.
• When I get wet and feel very cold, I easily catch a cold.

But the original sentence uses κάνει πολύ κρύο, which describes the weather/environment, not your personal sensation.

So:

• κάνει κρύο = the weather is cold
• κρυώνω = I feel cold

Both are possible in Greek, but they are not exactly the same.

Greek word order is fairly flexible, though some orders sound more neutral than others.

The original sentence is natural and neutral:

• Όταν βρέχομαι και κάνει πολύ κρύο, παθαίνω εύκολα συνάχι.

You could also hear variations such as:

• Όταν κάνει πολύ κρύο και βρέχομαι, παθαίνω εύκολα συνάχι.
• Παθαίνω εύκολα συνάχι όταν βρέχομαι και κάνει πολύ κρύο.

The meaning stays basically the same, but the emphasis may shift a little.

The original version is a very normal way to present:

1. the conditions first,
2. then the result.