A fork of Rural Dictionary
A fair weather friend is one who lives in a milder climate than you. This person takes great pleasure in taunting you with how great it is where they are (warm and sunny) when you are suffering in your climate (cold and snowy or otherwise unpleasant).
Shane was taunted by his fair weather friends on Facebook as he sat looking helplessly from his office window, watching snow fall in the middle of April in Michigan.