Humidity is a measure of the amount of water vapor in the air. It is a natural part of our atmosphere and comes from the amount of water vapor in the air. Water vapor enters the atmosphere by evaporating from the large bodies of water on the Earth’s surface including lakes, oceans, and seas. The higher the temperature, the more water vapor the air can hold. There are two types of humidity:

• Absolute humidity: This is the actual amount of water vapor in the air. The higher the amount of water vapor, the higher the absolute humidity.

• Relative humidity: This measures the amount of water in the air in relation to the maximum amount of water vapor (moisture) that the air can hold at a particular temperature. It is written as a percentage. Warm air can hold more water vapor than cold air, so with the same amount of absolute humidity, cold air will have a higher relative humidity and warm air will have a lower relative humidity. The relative humidity is 100% when the air is completely full of water vapor.

Humidity plays an important role in our daily weather. Without water vapor in the air, our weather might be like the weather on Mars. High humidity combined with hot temperatures is a combination that can be a health risk, especially for the very young and the very old. On the other hand, very low humidity can make us feel cooler than the actual temperature.

When you hear weather forecasters talk about humidity, you may hear them talk about two different terms: absolute humidity and relative humidity. Absolute humidity is the amount of water vapor divided by the amount of dry air in a certain volume of air at a particular temperature. The hotter the air is, the more water vapor it can hold. Relative humidity is the ratio of the current absolute humidity to the highest possible absolute humidity, which will depend upon the current air temperature. Relative humidity is the term weather forecasters use most often.