Don't use indoor cords outside—even under cover.

No.

Indoor extension cords aren’t built for moisture, temperature swings, or UV. Even under a porch or awning, humidity and condensation get in. Rain splashes. Spiders and mice chew on the insulation. The cord can degrade faster than you think.

The bigger risk: indoor cords usually don’t have a ground fault circuit interrupter (GFCI) built in. If water gets into a connection, you’re one step away from a shock or a fire. An outdoor-rated cord is a few bucks more and has thicker insulation, sealed plugs, and generally better protection.

Don’t gamble on “just this once.” Spend the $15.