Rear Window Blurry

Hi, it seems like whenever it rains or there is condensation on the car, my rear window seems to get blurry and I can't see out of it. If it's not raining and if there's condensation on the rear window, I sometimes turn on the rear-defrost and it'll clear up. It seems to be on the outside not the inside because when I turn on climate control, the front-windshield will clear up, but not the rear window.

It's almost like a thin film of water develops on the rear window. The water doesn't bead into droplets.

Any ideas?