What’s the difference between humidity and dew point? (Beau Wolf, Corydon)

Humidity and dew point are closely related and the two can be very confusing to the layman. Humidity is a percentage that is given to describe how “saturated” or “unsaturated” the air is with respect to moisture. At 100% humidity, the air cannot hold any more moisture and at which time condensation will occur. The lower the humidity value, the drier the air is and the more moisture it is capable of holding. The dew point can be described as the temperature to which a parcel of air would have to be cooled to before condensation will occur. The higher the dew point, the more moisture there is in the air. Note that the dew point will never exceed the temperature and that when temperature and dew point are the same, humidity is 100%. Also notice how humidity fluctuates wildly throughout the day while the dew point stays relatively constant. For instance, in the morning you may have a temperature of 70 degrees and a dew point also of 70 degrees giving you 100% humidity. By afternoon, your temperature may reach 90 while the dew point remains at 70. This produces a humidity value of only 55%.

Why does high humidity make us feel so uncomfortable? (Joe Arnold, Louisville)

The reason your body sweats during the heat of the day is to help you stay cool. As the sweat on your skin evaporates, it takes heat away from your body producing an affect known as evaporational cooling. Evaporational cooling is critical in keeping your body temperature at normal levels. Unfortunately, this process doesn't work nearly as efficiently when the humidity is high and can cause your body to overheat. The higher the humidity is, the less evaporation that can take place and the less cooling your body receives. When high humidity combines with high temperatures, as it often times does here in Kentuckiana, it can make it very difficult for people to function normally. At its worst, the combination of the two can lead to a heat exhaustion or even a heat stroke. So take it easy out there this summer, drink plenty of fluids and stay inside away from the heat when you can.