Maybe it's the humidity but the rear of my X is making it's own atmosphere...??
 

It's been on the humid side here in Houston the past few days. I notice when I give it a good acceleration, the rear windows fog up on the outside. As soon as I let go of the gas (no longer accelerating), the vapors goes away. I confirmed it's on the outside by using the rear wipers when it started to fog up.

Is this normal?

The hot air goes up which is why ive seen it happen on mine as well.

Forgetting the term but the back of the x while driving is a low pressure zone or something to with how the air acts(dont quote me on that).. Which is why the rear is always dusty first, or dirty even after a light drizzle and rest of car is clean.

That's one hell of a vacuum back there!