1996 Honda Accord EX sedan, 4 cyl. VTEC engine.
When driving in the rain and around 40-50 mph, a loud buzzing or vibrating sound suddenly comes from what seems to be the body or undercarriage. I have theorized it is the tires throwing water against the wheel well in a certain pattern, a loose piece of metal...but it only seems to happen in the rain. Can anyone suggest what the problem might be?

 

If it only happens in the rain, your idea about water shooting against something sounds good. Does it change when you go thru a puddle? How about when you drive over wet then dry areas of the road?

 

Once it starts, it doesn't seem to be affected by the amount of water on the road. And--I hate to say this--once or twice I have heard the same buzzing on a a dry day. I heard this question come up on "Car Talk" a year or so ago, but couldn't hear the answer.

 

Well if it wasn't for the rain connection, the first thing I'd check is loose heatshields on your exhaust system. Maybe the rain simply makes it easier to hear the rattling.