The switch is heating up and protecting itself like it was designed. For some reason only in the rain though.
You can replace the switch easy enough and or do the headlight relay mod.
89YJ 2.5L TBI, AX-5, NP231 SYE, Ford 8.8, Yukon Grizzly, Tom Woods Shaft, 33" BFG T/As, 4" lift, Warn VR10000s.
AF Jeep Club Tail #184