Rear windows won't seal tightly

[louwho99]

We have a 2008 Mobile Suites 38RLSB3. The problem we're having is that the rear windows (at the bottom of the large picture window) won't close tightly. Using the knob, we dial them all the way closed but the windows aren't "sucking in" and sealing. Today in Denver, we're having rain/snow/wind and the temperature tonight will be in the 20's. Wish we could move south, but that's not possible right now! If you sit on the couch, you can feel the cold wind blowing in. Any idea how to get these windows to seal tightly?

Thanks!