How much psi do tires typically loose when the weather gets cold and more, please read?

On my car, I have 3 different tire brands on. All of the tires have good tread. Last week when I checked my tires, 3 of them were either at 28-29 psi and one was at 26. This week I checked my tires, 3 were at 28-29 psi and the other one was at 22 psi. The tire that is low came from a junkyard and it is mounted on a 1995 Chevy Lumina 16 inch alloy rim with some corrosion (the other 3 are on aftermarket chrome rims). Does that tire leak air, or could it be leaking air because of the rim? Also, I live in the Cleveland,Ohio area and it snowed here on Friday night where I live.