take a look with a flashlight down at the camshaft inside the cover when you have the oil cap off...is there sludge all over the cam and head?....if not, then you may be okay with the condensation theory...if the sludge is all over the inside of the valve cover and cam....you have a bigger problem...
The motor creates heat and its colder outside. just like any container, the top of the valve cover where the oil fill cap is located will act like the top of a glass bottle, or even a 2 liter soda bottle...moisture will collect there and mix with the oil. The pcv valve will vent gasses (which now get recycled in the emissions system) but the engine has to heat up a bit for that process to take effect.
this amount of sludge in the short term is of little concern (if its condensation) but the sludge will begin to build up after time...and this is in fact bad for the engine...***after you confirm its only condensation and not a bigger problem***you have to take that baby out for a few spirited drives and get the temp up...heat up that sludge, mix it with the hot oil and it will begin to vaporize and escape through the emissions system.
Drive drive drive!