Ég athuga veðurspána áður en ég fer út.

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Breakdown of Ég athuga veðurspána áður en ég fer út.

• fara: to go
• áður en: before
• út: out

Questions & Answers about Ég athuga veðurspána áður en ég fer út.

Why is veðurspána ending in -na?

Because veðurspá (weather forecast) is a feminine noun, and here it’s definite (the forecast) and in the accusative singular.

• Indefinite nominative: veðurspá
• Definite nominative: veðurspáin
• Definite accusative: veðurspána
  The ending -na is the feminine accusative singular definite ending.

Why is veðurspána in the accusative case at all?

Because athuga (to check) is a transitive verb and takes a direct object, which in Icelandic is very often in the accusative. So athuga + accusative object is the normal pattern:
Ég athuga (eitthvað) → Ég athuga veðurspána.

How do I know athuga means “check” and not “investigate” or “examine”?

Athuga covers a range like check / look up / take a look at / verify, depending on context. With something like veðurspá it very naturally means check the forecast (similar to “check the weather app/forecast” in English). Other common options exist (e.g., skoða), but athuga is very idiomatic here.