I noticed squeaking on my passenger window a few days ago. The squeaking only lasted the final 2 or 3 inches until it was fully down. Rolling the window back up I had the same results; squeaked for the first couple of inches, then went silent.
Even though it hasn't happened again since, it got me wondering if anyone else experienced the same thing...and as it turns out, I'm not alone!
Oh and my window was completely dry and cool to the touch (if that helps).