What is the biggest sign that you should replace an extension cord?

If your extension cord feels warm to the touch after normal use, that’s the single most telling sign it needs to go. Internal resistance is building up, and that heat can lead to melting, arcing, or a fire. Also look for stiffness, brittleness, discolored or loose plug prongs, and replace any cord over a decade old. Don’t wait for sparks or a burning smell.