What happens to Rainbows

So, yesterday I pick Aiden up from school and off to Walmart we went to shop. When we came out of the store he spotted a puddle and for once didn't jump in it. He just stood there, pointed and said pretty. When I asked him what he was doing, he said he was looking at a rainbow. Then he told me what had happened. You see the puddle with the gas in it makes a rainbow of colors, but according to Aiden, the puddle was created because a rainbow fell from the sky and melted. On the way home he was quite concerned that there would be no more rainbows, because like the snow that is finally melting here, so are the rainbows. I reassured him that a rainbow only melts when it gets very old. Aiden then asked, does that mean winter is old and is going away. He so wants summer to come. I just love the innocents of children.