This depends on the solar lights. The best solar lights that are designated for the outdoors should fare just fine outside. A little water also won’t harm them. However, solar lights that are not properly sealed can become damaged by rain. If they are not specified to be water-resistant or waterproof, chances are that water can get inside and mar the internal light system. For this reason, you must never use indoor lights outdoors. Checking the product description also provides insight as to what conditions the solar light can endure.