Outdoor lights are safe in the rain, so long as they are rated and labeled for outdoor use. The light's plugs, connections, and light bulbs themselves should handle some level of weather resistance and waterproofing. However, we advise that you keep the lights and connections out of puddles! While some Christmas lights claim they're waterproof, I always worry about inclement weather - especially if the lights fall submerged under the winter muck, snow, sleet, and rain.