Okay, lets regroup:
He has 2 hours between drinking and going to bed, for the most part anyway. Yes, difficult and frustrating, but solvable. The fluids may take longer to travel to his bladder, you may have to restrict more than 2 hours in advance. Instead of liquids, you can use fruit, grapes, apples, whatnot for when he gets thirsty. Sugarfree candy can also help.
Okay, so it is cool there, especially in the evening, I used to live in Alaska, so I can relate. Don't you seem to have to go to the bathroom more often if you are cold? He may be a little chilly while sleeping at night. Make sure his room is a little on the warmer side.
They have the new overnight kids pants for kids his age and older that they can wear at night that keep sheets and clothes dry. This helps to eliminate embarrassment while you are working through this problem. You can make it something special between the two of you and the other kids don't need to know.
Check out this website, it is very interesting and may be helpful.
http://familydoctor.org/366.xml