The 0 deg rating info is out on the Keystone site, but its a bit of a pain to get to and you better have a high speed connection - its a large file. Go to the media page (
http://www.keystonerv.com/media.php### ) then click on Montana. One of the options you will see is a pdf for the 0 deg fact sheet. Click on that, then click on the agreement to keep the info secret for all time and then down load it.
My wife has been staying in our 3000RK several day a week for the past few months with temps down to 0 deg with no problems. One work of warning - they burn a lot of propane when its cold out.
Good luck.