ˌfair-weather ˈfriend noun [countable]
someone who only wants to be your friend when you are successful

[TahlilGaran] Dictionary of Contemporary English ▲

fair-weather friend
someone who is only your friend when you are happy and successful.
I had a lot of money and I knew a lot of people, but most of them turned out to be fair-weather friends.

[TahlilGaran] English Idioms Dictionary ▲

fair-weather friend
a person who is a friend only during good times
He is a fair-weather friend and you cannot rely on him if you have a problem.

[TahlilGaran] English Idioms Dictionary ▲

fair weather friend
n. A person who is a friend only when you are successful.
Everyone knows that John's only a fair-weather friend.

[TahlilGaran] English Idioms Dictionary ▲