You plug in the patio lights, they work for about ten minutes, and then — click — the whole outlet goes dead. You reset it. It happens again an hour later, usually right after a light rain or when the sprinklers kicked on. If this is your July, you’re not dealing with a broken outlet. You’re dealing with a GFCI doing exactly what it’s designed to do, just at the worst possible time.
The Short Version: Moisture Is Getting Where It Shouldn’t
Ground Fault Circuit Interrupters trip when they detect even a tiny imbalance in electrical current — the kind of imbalance that happens when electricity starts leaking somewhere it’s not supposed to, like into damp ground, a wet connector, or your hand. In winter, string lights sit dry and undisturbed. In summer, they’re getting rained on, soaked by dew, baking in the sun until the plastic housing warms and expands, then cooling and contracting again overnight. That constant cycle stresses seals and connectors until moisture finally finds a way in.
The GFCI isn’t malfunctioning. It’s catching a real, if small, leak before it becomes a real problem. The annoying part is that string lights are often just marginal enough to trip it without being dangerous enough to notice otherwise.
Where the Water Actually Gets In
- The male-to-female plug connections between light strands, especially if you’ve linked several sets together. Every connection is a potential entry point.
- Cracked or brittle bulb sockets, particularly on lights that have been reused for a few summers. UV exposure makes plastic casings go from flexible to crumbly.
- The outlet itself, if the in-use cover isn’t closing fully around the cord, or isn’t rated for outdoor use at all.
What Actually Fixes It
Drying everything out and hoping for the best only buys you a day or two. A few things make a real difference:
- Get the connections up off the ground. Water runs downhill, including down a drooping cord straight into a plug junction sitting in wet grass. Loop each connection point so it hangs slightly, or tuck it inside a small dry container.
- Use dielectric grease on connections. This is the same stuff used on trailer light wiring, and a small dab on each plug connection repels water without affecting conductivity. A tube like CRC Dielectric Grease costs almost nothing and solves this exact problem.
- Replace an outlet cover that doesn’t actually seal. A bubble-style cover that closes over a plugged-in cord, like this weatherproof outlet cover, is a different animal from the old flip-lid style that only protects the outlet when nothing’s plugged into it.
- Retire lights that are visibly cracked or chalky. If the plastic looks sun-damaged, it’s not sealing the way it did when new. Cheap fix, but only if you actually do it.
When It’s Not the Lights
If you swap in a brand-new set and it still trips within minutes, the problem may be upstream — a GFCI outlet that’s aging out, or wiring that’s picking up moisture somewhere it shouldn’t be at all. GFCIs do wear out over years of tripping and resetting. The Consumer Product Safety Commission recommends testing outdoor GFCI outlets monthly using the built-in test button, and if one won’t reset cleanly even with nothing plugged in, that’s a job for an electrician, not another trip to buy string lights.
Worth saying plainly: don’t disable or bypass a tripping GFCI to keep the lights on. It’s inconvenient, but it’s inconvenient on purpose. The alternative is a shock hazard sitting in your backyard during the exact season you’re most likely to be out there barefoot.
