noisy wiper blades
 

Last night it was raining (think of it as heavy drizzle... haha). I set the front wipers to auto, and I hear a faint sound that sounds like rubber rubbing when the wipers go up and down. Its not audible if you raise the radio volume up (not blasting), but knowing the noise is present is bothering me. When I use the wipers to wash the windshield when dirty, the noise is not present. Strangely, its only present when it rains.
Anyone else encounter this?