How do I tell if I've got gas?

I have a 22 Sport, which has the small propane gas tanks. There's some indication that the tanks might be empty (i.e., the fridge, on "gas," is giving that blinking caution sign). But they should both be nearly full, since the trailer has only been out twice. Is it possible that after two short outings, with only some minimal cooking and a little bit of refridgerating-while-traveling, that they would both be empty?



Anyway, how do I know? People say "weigh them," but that's kind of a pain in the butt, particularly since I don't know what they weigh empty or full. Someone else told me they get cold when they're empty, but I don't know how to tell when they're colder than they were before they were the temperature they are now.



So, I'm kind'a confused about what I'm looking at and what to look for, and any advice much appreciated.