If it is raining, just make sure that you put out crystals that are ok to get wet. For example, keep Selenite and Malachite inside because the rain will damage them. Crystals like the Quartz family (Clear Quartz, Amethyst, Rose Quartz, Citrine, Smoky Quartz) are all safe to be outside in the rain.
Swarovski recommends that you occasionally polish each piece with a soft lint-free cloth. If your jewelry is very dirty, wash your jewelry using warm water, a mild dish detergent and a soft bristled brush. Rinse thoroughly with clean water prior to drying with a soft lint-free cloth.