In sports, the term is often confused with a bandwagoner, but unlike bandwagon fans, a fair weather fan initially has some interest in the team, but they want nothing to do with them when tough times occur. As soon as the team starts to turn things around and starts winning, they act as if they been there through thick and thin.
A fair weather friend is more of an associate/acquaintance. They aren't truly your friend, but you talk to them enough to somewhat know them personally. They act nice to you when they need something, but as soon as you need them to return the favor, they are nowhere to be found. A true friend is there for you no matter what.
This term can be applied to anything in life, but these are the most common.
-Example of fair weather fan-
Me: The Lakers are on tonight, I can't wait
Fair Weather Fan: I can't wait either, they rock this year
Me: I thought you said acouple years back you were done watching them after ________ got traded and you couldn't stand all their mounting losses
Fair Weather Fan: Shh the games starting
-Example of Fair Weather Friend-
Fair Weather Friend: Hey I was absent last week, can I borrow your notes?
Me: Sure man, no prob
Fair Weather Friend: Cool man thanks. You wanna chill later on after your done with all your classes?
......Later on that day......
Fair Weather Friend: Thanks for letting me use your notes, i got a B on the test
Me: Its cool. So we still gonna hang out?
Fair Weather Friend: Huh, hang out? Nah man I can't, I got plans with other people
girl 1: i know.. he tried to rape me once :(
guy 2: fuck that shit, lets break his nose!
girl 1: yeah!
girl 2: don't guys he's really sweet! D:
guy 1: sweet until he's got his whole hand inside you..