Indoor Christmas lights will have a green UL listed tag, or a silver tag with the “UL” written in green. Christmas lights approved for the outdoors will have the UL listed tag in red, or silver with red writing.Click to see full answer. Correspondingly, can I use indoor Christmas lights outdoors?Using outdoor lights for indoor decorations is common and safe, but precautions must be taken if you are using indoor lights to decorate outside. Outdoor lights are made to withstand wet conditions and cold weather, while indoor lights are not.Furthermore, can indoor lights be used outside? While it’s generally safe to use an exterior light fixture indoors, the reverse isn’t true. You should not use an indoor light fixture outdoors in wet locations. They aren’t sealed against moisture and will stop working during the first heavy rain. Beside this, is there a difference between indoor and outdoor lights? Outdoor light bulbs are more variable. Typically, they are interchangeable for indoor and outdoor use. In contrast, indoor lights are not designed to withstand outdoor temperature changes.Can you leave Christmas lights on overnight?Christmas tree lights should not be left on for prolonged periods of time or overnight. Even LED lights can overheat, and with a combination of a dry Christmas tree, could cause a fire. Make it a habit to turn off your Christmas lights every time you leave the house or go to bed at night.