Water vapour present in the air is known as humidity.

It is expressed quantitatively in different ways.

The air containing moisture to its full capacity at a given temperature is said to be saturated.

It means that the air at the given temperature is incapable of holding any additional amount of moisture at that stage.

The temperature at which saturation occurs in a given sample of air is known as dew point.

Humidity is, in general, a measure of water vapor in the air.

What is water vapour?

Water is a super special substance. It is basically everywhere on Earth – in our soils, our oceans, and our air.

Water exists in three states – liquid, solid, and gas.

Liquid water helps hydrate us during a hot day or after a long sports game.

Solid water, or ice, is colder and gives us a surface to ice-skate on.

Water in its gas form is water vapor, or moisture.

There is water vapor in our atmosphere because of evaporation.

Evaporation happens when water changes from a liquid to a gas.

Liquid water evaporates from oceans, lakes, rivers, plants, the ground, and fallen rain.

What is absolute humidity?

The actual amount of the water vapour present in the atmosphere is known as the absolute humidity.

It is the weight of water vapour per unit volume of air and is expressed in terms of grams per cubic metre.

The ability of the air to hold water vapour depends entirely on its temperature.

The absolute humidity differs from place to place on the surface of the earth.

The higher the amount of water vapor, the higher the absolute humidity.

What is relative humidity?

Relative humidity also measures water vapor in the air, but it is compared to the maximum amount of water vapor that can exist in the air at its current temperature.

The percentage of moisture present in the atmosphere as compared to its full capacity at a given temperature is known as the relative humidity.

It is written as a percent.

With the change of air temperature, the capacity to retain moisture increases or decreases and the relative humidity is also affected.

It is greater over the oceans and least over the continents.

For example, warm air can hold more water vapor, or moisture, 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.

What is dew point?

The dew point marks the temperature at which water vapor will turn into liquid water droplets.

This process is called condensation. Condensation is what causes clouds to form, which can then lead to precipitation such as rain, snow, and hail.

The dew point will always either be the same or lower than the actual outside temperature.

The higher the dew point rises, the greater the amount of moisture in the air. This affects how “comfortable” it will feel outside.

How does humidity affect our weather?

Basically, the more water vapor in our atmosphere, the more possibility of precipitation.

Precipitation happens when the air rises and causes condensation of water vapor into liquid water droplets.

This is the beginning of the formation of precipitation.

These little droplets grow through a process called “collision-coalescence”.

During collision-coalescence, these droplets come together and form larger drops.

Once the drops are a certain size, they become too heavy for the air and the drops fall as precipitation from the clouds.