My bedroom is the hottest room in the house, and even with all the windows open and fans in them doesn't cool off as much as I would like when it's an acceptable temperature outside. And I prefer to sleep in a rather cool room since I find it easier to breath.

I have a window air conditioner that works perfectly in the summer, keeping the room nice and cool. But in the spring and fall, when it's cool outside (but not cool enough for me to be comfortable!) the AC will freeze over quickly.

What can I do to prevent it from freezing?

Are some window air conditioners better at working with lower outside temperatures? If so what would I be looking for?