Am I correct in assuming that the phrase was inspired by The Wizard of Oz? Or did it come from somewhere else and a witch being melted by water happened to co-opt it?
I always heard it as “you won’t melt, you’re not made of sugar”.
My mother used to say either “you’re not a witch”, or “you’re not made of cotton candy”. So I don’t think the phrase is directly from The Wizard of Oz. They’re just chiding the unwilling rain-goer, asking what the consequences would be.
I’ve been out in the rain with bona fide witches. They didn’t melt. Some of 'em got mad, though.
Obviously, they weren’t as bona fide as you thought. 
It was meant in that context first. I believe that the shortened version started being confussed with with the OZ series.
I think that it may have had more to do with spun sugar, such as cotton candy, witch melts away on a humid or rainy day.
A variation is “If you’re made of sugar, you’ll melt, if you’re made of shit, you’ll float”. Like a “turd floater”.
My response to them: “Did you see Alien Nation?”
I don’t do rain.
AHunter3 It rains saltwater in New York?
If you have hair like mine, though, you will look like a ball of cotton candy…
I remember reading a science fiction short story (by Isaac Asimov I think) that had a strange family living next door with the name of Sakharov. One day the child protagonist notices the family running home to avoid the beginning rain, but don’t reach the front door before the storm bursts - you can imagine the sad ending.
Ah, thanks. Cotten candy predates the movie by some 30 years.
In my family, the saying typically goes “You’re not sweet enough to melt, nor old enough to rust”. Of course, there was also a rusty character in Oz…
There is also “you’re not made of chocolate: you won’t melt”.
You know, it’s always bothered me that the Tin Woodsman would have a problem with rust.
yeah, yeah. I’ve heard the excuses – Tin corrodes, too (although I’ve never heard it called “rust”). Or they used iron or steel fittings that rusted. Or whatever. I still think that a tin guy shouldn’t “rust”. They shoulda galvanized him.
Yeah, I read that . . .
I never did see the point of the story.
I always heard it “You’re not made of salt; you won’t melt.” I always assumed that was a reference to Lot’s wife being turned into a pillar of salt.
How weird is that?!??
The proper response is “I may not be a witch but I still wouldn’t want a house to fall on me.”
I think, like “Shah Guido G.”, it was just a shaggy dog story. it was a weird one though.
There are a few references to the date of the movie. It shouldn’t be forgotten that the book The Wizard of Oz by Frank Baum was published in 1900. Unless the melting is original to the film, the date of the movie has no real significance.