Yes, it's that phase change from liquid to gas that's the problem with using air containing a significant amount of water. Say you fill your race car tires on a hot humid day. The next morning the tires will be much cooler and some of the water vapor in the humid air has now condensed inside the tire therefore dropping the pressure more than would be expected by the ideal gas law. Then you top off the tire to get it up to just the right pressure, but it still has some of the condensed liquid water inside. So when the tire heats up during the race that water turns into gaseous water vapor and the pressure of the tire becomes greater than intended for optimum traction and handling.