Why does outdoor gfci keep tripping?

So how do you know which one? Moisture buildup is another major cause of GFCI firing. Outdoor installations are the most vulnerable and rain is the most common cause. However, due to Florida's tropical climate, high humidity can also cause moisture to build up and make it difficult for water trapped in a receptacle box to evaporate. Ground faults occur when electrical current finds an involuntary path to ground.

Common ground fault suspects include worn insulation, conductive dust, water, or other soft terrain. Ground faults account for more than 80% of equipment short circuits and in 90% of these cases they are caused by deterioration of the insulation of wires and cables. If a human becomes the unwanted path, a current as low as 75 mA can trigger ventricular fibrillation (that is, there are several different reasons why a GFCI turns off. The most common reason is water or moisture that has entered the receptacle box or outlet.

However, a GFCI device that disconnects could also be caused by an overloaded circuit, a malfunctioning outlet, electrical problems, or improper installation. The cable may rot or there may be moisture in the outdoor outlet. If a GFCI deactivates, it deactivates because there is a current leak. You can try to go inside the box of the GFCI, disconnect the cable coming out to the outside and see if it still triggers, if you don't have a problem with the external wiring, if it keeps firing, you should replace the GFCI.