Never use indoor extension cords outside, they are not built for such rugged use. Do NOT leave even your outdoor extension cord outside more than a day or two. Left outside over extended periods, cord materials can breakdown, potentially resulting in sparking, fire, and shock.Click to see full answer. Also know, can you use an indoor extension cord on a covered porch?Extension cords are the perfect solution when you need to power a device whose cord doesn’t reach an outlet. An outdoor extension cord can be used indoors, but you should never use an indoor extension cord for outdoor tasks. Knowing the difference indoor and outdoor cords will help you eliminate safety hazards. can indoor extension cords get wet? The extension cords used indoors are made for that. They’re usually light and flexible, so they’re easy to keep out of the way. And they’re definitely not made to stand up to getting wet. Buy and use only outdoor-rated extension cords for any temporary lighting you’re connecting outside your house. Considering this, how can you tell if an extension cord can be used outside? How to Tell If an Extension Cord Is for Outdoor Use | Mr. Electric The letter “W” on the packaging or the cord itself indicates a cord that is designed for use outside. The primary difference between an indoor extension cord and an outdoor cord is the insulation. While many indoor extension cords have two-prong plugs, outdoor cords always have three-prong plugs. Are all orange extension cords for outdoor use?W indicates a cord designed for outdoor use. The biggest difference between indoor and outdoor extension cords is the insulation. Outdoor versions have bright orange rubber, plastic, or vinyl covers, while indoor cords are much less heavy-duty. J means the cord has standard 300-volt insulation.