Tires always mysteriously "lose" air in the colder temps. There's a jury out on whether it is the same air, just colder, thus less expansion. Or whether it actually leaks out somewhere. I have to go around to all the trailer tires(which have steel wheels), in the fall, and tighten all the valve stems/caps or my tires start to leak. Once I do that, they're good for the winter. My thoughts are, that we get both problems, just like everything else in the cold, low temps bring out all the gremlins. Just remember to fill them when they're cold, and check them often!
