5 Things to Know About Extension Cord Weather Ratings

A ‘W’ at the end of the cord code means weather-resistant. The letters printed on the jacket, like SJTW or SJOW, are standardized codes that tell you the cord’s material and intended use.

SJTW stands for junior hard service, thermoplastic, and weather-resistant. This cord is designed to handle moisture, sunlight, and temperature swings outdoors.

SJOW is similar but adds oil resistance. Use this cord where exposure to oils or chemicals is a concern.

Cords without a ‘W’ are indoor only. Codes like SJT or SVT lack weather protection. Running them outside will cause the insulation to degrade quickly and let water in.

Always check the jacket code before using a cord outdoors. Don’t guess—the code tells you everything you need to know about where the cord is safe to use.