fair-weather friend
US /ˈferˌweð.ər ˈfrend/
UK /ˈferˌweð.ər ˈfrend/

1.
amigo de tempo bom, amigo interesseiro
a person who is only a friend when things are going well and abandons you when difficulties arise
:
•
I thought he was my friend, but he turned out to be a fair-weather friend when I lost my job.
Eu pensei que ele era meu amigo, mas ele se revelou um amigo de tempo bom quando perdi meu emprego.
•
Don't rely on him; he's just a fair-weather friend.
Não confie nele; ele é apenas um amigo de tempo bom.