Ice in my oil?

[CoBeerToad]

Saw I was a on the low side of oil and went to add some more in. There was this brown crusty stuff inside the cap and a bit on the filler nozzle. Upon closer inspection, I determined that it was ice. (It's been in the -10s for a couple days here) Not a lot of ice, but it doesn't take too much ice in my oil system to scare the hell out of me. Why is there ice under my oil cap? Perhaps condensation? I just back from from driving from OKC to Chicago and I parked it and haven't touched it in a week. Please say normal condensation. Please say normal condensation.