Have you ever visited a place that just made you feel hot and sticky the entire time, no matter what you did to cool off? You can thank humidity for that unpleasant feeling.

Humidity is the amount of water vapor in the air. If there is a lot of water vapor in the air, the humidity will be high. The higher the humidity, the wetter it feels outside.

On the weather reports, humidity is usually explained as relative humidity. Relative humidity is the amount of water vapor actually in the air, expressed as a percentage of the maximum amount of water vapor the air can hold at the same temperature. Think of the air at a chilly -10 degrees Celsius (14 degrees Fahrenheit). At that temperature, the air can hold, at most, 2.2 grams of water per cubic meter. So if there are 2.2 grams of water per cubic meter when its -10 degrees Celsius outside, were at an uncomfortable 100 percent relative humidity. If there was 1.1 grams of water in the air at -10 degrees Celsius, were at 50 percent relative humidity.

When humidity is high, the air is so clogged with water vapor that there isnt room for much else. If you sweat when its humid, it can be hard to cool off because your sweat cant evaporate into the air like it needs to.

Humidity is blamed for all kinds of negative things, including mold in your house (usually the bathroom, where its wet a lot of the time), as well as malfunctions in regular household electronics. Moisture from humid air settles, or condenses, on electronics. This can interrupt the electric current, causing a loss of power. Computers and television sets can lose power like this if not protected from the effects of humidity. Living with humidity is easier with the aid of a dehumidifier, which sucks moisture out of the air.

High humidity is also associated with hurricanes. Air with high moisture content is necessary for a hurricane to develop. U.S. states such as Texas and Louisiana, which border the very warm Gulf of Mexico, have humid climates. This results in tons of rainfall, lots of flooding and the occasional hurricane.

humidity
Tropical waterfalls are humid places.

The Not-So-Hot Zone
People are usually comfortable at 45-percent relative humidity.

Noun

all weather conditions for a given location over a period of time.

dehumidifier
Noun

device that pulls moisture from the air.

evaporate
Verb

to change from a liquid to a gas or vapor.

Noun

overflow of a body of water onto land.

Noun

amount of water vapor in the air.

hurricane
Noun

tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.

malfunction
Verb

to not work correctly.

moisture
Noun

wetness.

mold
Noun

hollow structure used to give form to a liquid substance as it hardens.

rainfall
Noun

amount of precipitation that falls in a specific area during a specific time.

relative humidity
Noun

ratio between the amount of water vapor in the air and the air's saturation point. Relative humidity is expressed as a percentage.

vapor
Noun

visible liquid suspended in the air, such as fog.