Learn Icelandic: Það er rigning og vindur í dag.

Það is acting as a dummy subject. Just like we say 'It is raining' or 'There is rain' in English, Icelandic sentences usually need a subject. When talking about the weather or general situations where there isn't a specific person or thing doing the action, það steps in to fill that empty spot.

Does það er mean 'it is' or 'there is'?

It can mean both! Það literally translates to 'it,' but in sentences like this, English speakers often translate það er as 'there is.' Icelandic uses this exact same structure whether you translate it as 'It is raining' or 'There is rain.'

Are rigning and vindur adjectives like 'rainy' and 'windy'?

No, they are nouns meaning 'rain' and 'wind.' While English often uses adjectives to describe weather ('It is rainy'), Icelandic very commonly uses nouns with það er to say literally 'There is rain and wind.'

Why is 'today' written as two separate words (í dag)?

In Icelandic, 'today' is expressed with the fixed phrase í dag, which literally means 'in day' or 'into the day.' It is always written as two words, similar to how í kvöld is used for 'this evening' or 'tonight.'