Does a baseball travel farther when hit in humid weather conditions? If so, what scientific principles are at work?

You might think that a baseball (or another type of ball) would not travel as far on humid day due to the moisture in the air--but just the opposite true. The air may feel "heavier" on a muggy day ,but it is not any denser; in fact, it's slightly lighter! (The sticky uncomfortable feeling most of us experience on this type of day is due to condensation hindering the evaporation of perspiration.)

When it's humid, water molecules replace the heavier oxygen and nitrogen molecules in the air. Humid air weighs less than dry air at the same temperature and pressure. Under such conditions, moving objects encounter less drag, although the difference is rather minor. On a day when the temperature is 86 degrees Fahrenheit (30 degrees Centigrade) and the relative humidy of 80 percent, the difference in density has been calculated to be about 1%. There is also a limit to how much water vapor the air can hold (and how much of a factor humidity can play), a relative humidy of 100 percent means the air is completely saturated.