I think the best place to begin is to look at what these prepositions stand for. "On" in relation to time refers to a specific time. "In" in relation to time can be read as "during". So as for your example On November is incorrect since , whilst November is a specific month we have no idea when in the month you are referring to. As Alan said, you can say "On November 14th....." but you have now specified a specific time. In November is absolutely fine since it can be read as "During November .........."

In November, I will go on vacation. (The speaker does not specify which day; but it will be some day in November.) On November 14th, I will go on vacation. (The speaker specifies the exact day.)