Translation:It is raining.
Another definition of 오다 is for rain or snow to fall down from the sky. So it's not correct to translate it as, "rain comes."
I think it should not be continuous tense. It should be present simple tense. "It rains."
Short, present simple tense intransitive constructions are not favored in actual use in US English, at least. I would never say, "it rains." It feels antiquated, robotic and clipped to me. When I use similar constructions in other languages my brain wants to "fix" it with the progressive cause they feel synonymous.