Jag går sällan ut när det regnar.

Not necessarily. Gå often means go in Swedish, not just walk.

In Jag går sällan ut, går ut means go out / go outside, not specifically walk outside. In many everyday contexts, Swedish uses gå where English would simply say go.

So here, Jag går sällan ut is best understood as I rarely go out.

Sällan means rarely or seldom.

In a main clause, Swedish frequency adverbs like ofta (often), alltid (always), and sällan usually come after the finite verb:

• Jag går sällan ut.
• Hon kommer ofta hit.

That is why sällan comes after går.

Because gå ut is a verb + particle combination, similar to a phrasal verb in English.

• gå = go
• ut = out

Together, gå ut means go out.

Swedish often keeps these as separate words. So:

• Jag går ut = I go out
• Vi gick ut igår = We went out yesterday

När usually means when, but in sentences about habits or repeated situations, it can feel like when/whenever in English.

So när det regnar means:

• when it rains
• or more naturally in context, whenever it rains

It is not quite the same as om (if).
Compare:

• Jag går sällan ut när det regnar. = I rarely go out when/whenever it rains.
• Jag går inte ut om det regnar. = I do not go out if it is raining / if it rains.

Swedish uses det as a dummy subject in weather expressions, just like English uses it:

• Det regnar. = It is raining.
• Det snöar. = It is snowing.

The det does not refer to a specific thing. It is just required grammatically.

Because Swedish often uses the present tense for general truths, habits, and repeated situations.

Here, när det regnar means when it rains / when it is raining, in a general habitual sense.

So the present tense works naturally because the sentence describes what the speaker usually does in that situation.

You could, but it sounds less natural than Jag går sällan ut när det regnar.

Why?

• sällan directly means rarely
• inte ofta means not often

Both can be understood, but sällan is the more natural and idiomatic choice here.

Yes. The word order is very natural Swedish:

• Jag = subject
• går = finite verb
• sällan = adverb
• ut = particle
• när det regnar = subordinate clause

So the structure is:

Subject + finite verb + adverb + particle + subordinate clause

A native English speaker may want to place sällan somewhere else, but Jag sällan går ut ... is not correct in normal Swedish.

Yes. If you move that part to the front, Swedish changes the word order in the main clause:

• När det regnar går jag sällan ut.

This is because Swedish follows the V2 rule in main clauses: the finite verb usually comes in the second position.

So after the fronted clause När det regnar, the verb går comes before the subject jag.

A common negated version would be:

• Jag går inte ut när det regnar. = I do not go out when it rains.

Notice that inte comes after the finite verb går in the main clause.

If you wanted to negate the subordinate clause instead, you would say:

• Jag går sällan ut när det inte regnar.

That means I rarely go out when it isn’t raining, which has a very different meaning.

Yes, usually a little.

• sällan = rarely / seldom
• inte ofta = not often

Sällan sounds more direct and more idiomatic. It suggests low frequency more clearly.
So in this sentence, sällan is the best natural choice.

Regnar is the present tense form of regna (to rain).

Swedish present tense often uses -r:

• regna → regnar
• komma → kommer
• bo → bor

So regnar simply means rains / is raining, depending on context. Swedish does not need a separate -ing form the way English does. The plain present tense can cover both ideas.