What causes wiper blades to squeak?

Answer 1

Usually when the wipers are dry and have no water (rain) to lubricate the blades. It also could be that the rubber blade is folded over.

Squeaking, vibrating and bouncing is commonly called "chatter". It can be simply a byproduct of dry wipers on dry glass (no water (rain) to lubricate the blades). Most commonly and most likely however it's a sign of worn wiper blades that need to be replaced. As rubber gets older, it stiffens up and loses its flexibility and thus chatter begins. The last possibility, however unlikely, your wiper arms may be slightly twisted meaning that the wiper blade is not perfectly 90 degrees to the glass so the wiper blade doesn't properly "flop over" from side to side as the wiper arm sweeps. There are ways to adjust this, but I'd recommend starting with new wiper blades first and then looking into adjusting the arms if the chatter still persists.