det regnar

Swedish requires a subject in most sentences. For natural phenomena like weather, where there's no specific 'doer', the pronoun 'det' (it) fills the subject role. This is sometimes called a 'dummy subject' or 'formal subject'.

The basic pattern is:
det + verb

For example:

• Det regnar. (It is raining.)
• Det snöar. (It is snowing.)
• Det blåser. (It is windy/blowing.)
• Det åskar. (It is thundering.)

This pattern works in different tenses, following standard verb conjugation rules.

Past Tense:

• Det regnade i går. (It rained yesterday.)

Future Tense:

• Det kommer att snöa i morgon. (It is going to snow tomorrow.)

Note that this is different from using adjectives to describe the weather, which uses the det är pattern (e.g., 'Det är soligt' - It is sunny).

Position And Omission
Regnar det? is a full yes/no question. I dag regnar det is a statement beginning with a time phrase. Keep det in the appropriate subject position rather than assuming every weather sentence begins with it.

Short notes and conversational replies may omit an understood initial subject: Regnar i dag can be an abbreviated weather comment. Use Det regnar i dag as the neutral complete-sentence model. Other weather descriptions name an actual subject, as in Solen skiner; det is not required in every sentence about weather.