It's raining or it's snowing? Is what I answered, which is the same question as the answer that DL put. It should be accepted.
'Il pleut' translates to 'It is raining.' If you want to translate word for word, 'Il' = 'It' and 'pleut' = 'is raining.' In French, there's no difference between 'It rains' and 'It is raining' because they're both in the present tense. The 'is' is part of the verb so to speak.
But yes, the reason the translation is 'is it' instead of 'it is' is because it's a question. They're both technically valid, it just depends on your intonation, whether you say 'It's raining.' or 'It's raining?'
I wrote: it is raining r snowing with a question mark... marked wrong? why on earth!!!!!!!!!!!
I can see saying in disbelief one of the two: "It's snowing?!" or "It's raining?" but "It is raining or snowing?" would be a stretch for usual English.
il pleut ou il neige ? , more natural, with an interrogative intonation !
pleut il ou neige t-il ? more formal but often uses for writting !