Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello, since it's doing it in wet conditions it's most likely an exposed wire in the running light harness that shorts to ground when it's wet and pops the fuse.
Not long ago this type of short was hard to find and was pretty time involved, thanks to newer technology that's not the issue now. What you need to do is find a shop that has a thermal imaging camera. They can run the vehicle through a car wash to simulate the condition and use the thermal camera to detect the high amperage draw from the short.