a friend when circumstances are pleasant or profitable
Yep, and they are nowhere to be found when you need help!
fair weather friends are the worst kind to have.
No, the worst ones are the severely neurotic who always misinterpret what I say, or jump to conclusions, and then it is not even worth trying to explain to them, because they just want to argue anyway. And I think it is just because he is eloquent; people who are eloquent are the worst friends to have, because they like to be confrontational because they know they can win most arguments. Ah, the hell with it, everyone can just leave me alone!
Okay, so the important thing is to make a thesis statement that is unique or useful enough to be worth saying. It would be no good to say, "Fair weather friends disappear when you need them most," because that is just saying what a fair weather friend is.
The purpose of an essay is to expound one idea... the kind of idea that requires some explanation.
For example, I might say something about the fact that people may call you a fair weather friend when, actually, they are the kind of person who constantly asks for favors and people can't afford not to avoid them. This idea would require an explanation.
One essay = one big idea
Put the idea in a single sentence at the end of the first para, and make the rest of the paragraphs about sub-ideas that help explain the main idea.
Thanks for participating here!