Don't leave SJTW cords in direct sunlight.

No, you should not use a standard SJTW extension cord in direct sunlight for extended periods.

The “W” in SJTW stands for “weather-resistant,” but that mostly means it handles rain and moisture—not continuous UV exposure. The ambient temperature rating is typically -40°C to 60°C (-40°F to 140°F). Direct sunlight can push surface temps well above that, especially on dark pavement or rooftops. Even if the ambient air is cooler, the cord’s jacket absorbs heat and can exceed the rating, softening the insulation or causing cracking over time.

UV degrades the thermoplastic jacket. It gets brittle, cracks, and eventually exposes wires. You’ll see it happen within a season or two if the cord sits in full sun daily. For permanent outdoor use or anything that gets sun all day, get a cord rated for sunlight exposure—look for SJOOW or SOOW (the extra “O” means oil-resistant, but they usually have better UV stabilizers too) or anything with a “sunlight-resistant” tag.

For occasional or short-term use in sun, an SJTW will survive. Just don’t count on it for years.

Better to spend a few extra bucks on the right cord than to chase a short circuit later.