Sit start in the centre of the groove, make a strong move up to crozzly slopers, and move right to a good hold on the arete. Keep it together for the topout.
Rain sucks, but broken holds suck even more. Remember, never climb on wet rock in Fontainebleau.
The sandstone becomes brittle, and pulling on it will ruin classic problems. Drying it doesn't help, because it's still wet and weak inside.
All you can do is wait for better conditions.