Interlaken maybe not?

Booked to go to Interlaken very soon but the weather forecast at this point is pretty wet. Concerned that we won't be able to make the most out of what will be a pretty expensive ten days, vignettes, Jungfrau pass etc. and see the area especially to go up the Jungfrau which is a long held dream. Can't decide whether to just go for it or to bail out and seek the sun in the south of France?