Learn Finnish: Sataako ulkona? - Is it raining outside?

In English, we use a dummy subject for weather and say Is it raining?. Finnish does not do this. You simply use the weather verb on its own, so sataako is enough to ask Is it raining?.

How does the question ending work in sataako?

To turn a verb into a yes/no question, Finnish attaches the clitic -ko or -kö directly to the verb. sataa means it rains, and adding -ko makes it sataako, meaning is it raining?.

Since this lesson is about negation, how would I say it is not raining?

You would say ei sada. For Verb Type 1, the negative form uses the negative verb ei plus the weak stem of the main verb. The strong t in the verb sataa weakens to d, giving us the negative stem sada.

Does the ending on ulkona mean anything?

ulkona means outside. You might recognize the base ulko- from words related to outdoors. The -na ending is part of a grammar case you will learn later, but for common location words like ulkona and kotona (at home), it is best to just memorize them as fixed vocabulary words right now.