A really bad set of spark plug wires, or a really
really bad cap will not like water in the engine bay. The relay board, if you don't have the cover, will also not like lots of water in the engine bay--like a car wash. It's fine with the cover on the board, though.
If you drive over 35 MPH, very little if any water will get into the engine bay. Or the cockpit, if you happen to leave the roof at home...
(Don't ask how I know that!
)
--DD