try this next time it's rainy: park the car in a very dark place like your garage, open the hood, turn off all lights and watch for any elect. arcing. It helps if it's really dark. YOu could have a crack in the elect.ignition cover that causing a short or spark is arcing from spark-plug cable. Be very careful you don't stick your hand in the radiator fan; Messing around a running engine in the dark is pretty dangerous. I can't figure out what the noise is, and why it only happens when it rains. It kind of sounds like the car has glass packs on it! It will do it and then stop for a while, and then do it again. Any suggestions would be greatly appreciated Thanks.