How can I hold my Christmas lights from popping my GFIs during stout rain? ...
Answers: It sounds like you enjoy your extension cords laying across the ground and getting drizzly. You have to save them off the ground and out of the river
This is obviously cause by leakage currents through drizzling conductors. Try taping any connections (plugs and sockets) that are exposed to precipitation.
If it can't be stopped, try moving the lights to a circuit without a GFI