I'm not sure what size propane tanks I have. I think they're 5 gallon? Just standard tanks. My trailer came with 2 larger ones but I can hardly lift them when empty, so I stayed with the smaller ones. I also had a one gallon one, which is hard to find, but I needed two in the back of my truck - one for cooking and one for heat (I used a propane heater). I know, I know, but when you're living in a truck, you take the chances and risks you have to take. I wanted hot food and I was tired of being cold all the time.
Anyhoo, the 5 gallon ones are now the ones I use for the trailer I'm living in and they're out in direct sun for at least part of the day in summer. One summer it got up to 115° here, and there was no problem with the tanks.