Fasching (or Karneval, or Fastnacht, as it's called in some areas) is somewhat similar to Halloween in the US, especially if you look at the costumes and all the sweets that are handed out. But in other things it couldn't be more dissimilar.
For once, Fasching is a very serious event. In some areas it's political - nothing can get more serious than that. It has traditons - according to Wikipedia (and we all know if it's in Wikipedia, it must be true) it goes back to the 13th century, possibly even longer.
On the other side, it's about having fun, being somebody different for a short while and gourging yourself one last time before Lent starts.
In the little town I've grew up the traditional parade happens on Tuesday - and as far as I can recall we never had bad weather on that day. It may have rained on Sunday on the parade in Frankfurt, or snowed on the big parade in Mainz on Monday - we had neither (not always sunshine and rarely warm, as this is usually February, but no rain or snow)
So I went out and watched purple cows pass by.