If You're in the Northern Hemisphere, "... a blizzard in July"; if you're in the Southern Hemisphere, change "July" to "January". But I have a hunch that if you use the same idiomatic expression in every essay, adding one, two, or even three alternatives into a rotation is not going to satisfy the teacher for very long. Any of the likely alternatives to the idiom are going to be somewhat informal, so in more formal writing you might want to use a phrase like "highly unlikley" or some of the choices of Armen.

Alternatives of 'a snowball's chance in hell'
I want to to know how to change questions to indirect speech if we are asking about personal information? E.g "What's your name?" said John to the man.
"How old are you? 
What's your job? 
