You hear about it all the time in the weather reports. It's to blame for that muggy, steam-room feeling you experience on certain days. It's called humidity.

­WHAT DOES THIS GRAPHIC SHOW?

The graphic above shows the dew point and the relative humidity at 2:00 PM for today and tomorrow. The map on the right shows humid air (in green) and dry air (yellow/white).

The DEW POINT is the temperature air would have to be cooled to form dew. To make it simple, what you need to know is the higher the DEW POINT number, the more moisture that's in the air.

RELATIVE HUMIDITY, in simple terms, is the amount of water vapor in a column of air.

A reading of 100 percent relative humidity means that the air is totally saturated with water vapor and cannot hold any more, creatin­g the possibility of rain.

This doesn't mean that the relative humidity must be 100 percent in order for it to rain -- it must be 100 percent where the clouds are forming, but the relative humidity near the ground could be much less.­

IMPACT ON OUR HEALTH

STAYING COOL ON A HUMID DAY
Humans are very sensitive to humidity, as the skin relies on the air to get rid of moisture. The process of sweating is your body's attempt to keep cool and maintain its current temperature.

If the air is at 100-percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high.

If the relative humidity is low, we can feel much cooler than the actual temperature because our sweat evaporates easily, cooling ­us off.

HUMIDITY AND FRIZZY HAIR
Any lady can tell you humidity has a major impact on their hair. The higher the relative humidity, the more frizzy the hair. The lower the humidity, the more tame the hair.

The length of a strand of human hair changes with different relative humidity. As the relative humidity increases, hair becomes longer, and as the humidity drops it becomes shorter.

On very humid days, your hair actually becomes longer and this extra length causes the frizziness that gives us bad hair days.

HOW TO READ THE GRAPHIC

The graphic shows the dew point and relative humidity at 2PM Today and Tomorrow. This can be used to detect just how muggy it will be. The higher the dew point, the more muggy it will be.