someone who is unreliable, especially in times of trouble

अविश्वसनीय व्यक्ति

English Usage: He was a fairweather friend, only around when things were good.

Hindi Usage: वह एक अविश्वसनीय मित्र था, केवल तब ही आता जब सब कुछ अच्छा होता।

describing conditions that are pleasant and good only when things are going well

सुखद स्थितियों का वर्णन जो केवल तब होती हैं जब सब कुछ ठीक चल रहा हो

English Usage: They only enjoy outdoor activities during fairweather seasons.

Hindi Usage: वे केवल सुखद ऋतुओं में बाहरी गतिविधियों का आनंद लेते हैं।