A fair-weather friend changes with the wind.
More Spanish Proverbs:
A good word extinguishes more than a pailful of water.Spanish
Who is to carry the cat to the water?
Spanish
Wipe the nose of your neighbour's son, and marry him to your daughter.
Spanish
Always taking out and never putting in, soon reaches the bottom.
Spanish
He who eats and puts by, has sufficient for two meals.
Spanish
Don't spoil the ship for a halfpenny-worth of tar.
Spanish