Bookmark added to your notes.
View Notes

What is Dew?

You might have seen on hilly areas, tiny drops rest on the cool surfaces at night. Also, you might have seen beautiful shiny drops on leaves during winters. Do you know what these two statements pertain to?

Well! We find dew on the cold surfaces and dewdrops form on the grass in winter that’s why we find a lustrous view on leaves.

So, do you know the following things?

  1. How dew is formed? 

  2. How to dew?

  3. Use of dew gauge to know about dew.

  4. Difference between dew and fog

If not, this article will discuss how dew drops are formed with a dew factor and how to distinguish between dew and fog.

How are Dew Drops Formed?

We all are surrounded by air. This air contains moisture during the monsoon. At his moment, we call this air the humid air. 

Now, when there is a temperature rise, this temperature rise leads to the evaporation of water, and the evaporations result in the formation of water vapours.

So, we understood that around us contains water vapours which we call moisture or humidity. Hot air contains more moisture as compared to cool air. During the chilled night when the hot air comes in contact with the cold surface, water vapour present in it condenses and takes the form of droplets, which is the exact dew definition.

In simple words, the hot air condenses and form tiny droplets that make a coating on the cold surfaces and the leaves of the grassland. A beautiful scenic view of the dew is shown below:

[Image will be uploaded soon]

Now, let’s understand the science behind the formation of dew:

Formation of Dew

Water vapour condenses into droplets relying on the temperature. The temperature at which droplet formation occurs is called the dew point. When the surface temperature drops, gradually reaching the dew point, atmospheric water vapour condenses to form small droplets on the surface, and that is how dew drops are formed. 

From the above text, we understood how dew formed. Now, we will distinguish between dew and frost.

Difference Between Dew and Fog

So far we understood what is dew, but we are still left with the concept of fog. 

Fog is a mist that we encounter while driving on hilly roads. We also hear in the news that due to the fall of an iceberg, the temperature may lower and that is the time when the days are unclear and mist tightly hugs the mountains. The unclear vision we find in the below image is the fog:

[Image will be uploaded soon]

The process of the formation of dew distinguishes it from hydrometeors, i.e., meteorological occurrences of water that form directly in the air that cools to its dew points (around condensation nuclei), and this is called the fog or frost. The thermodynamic principles of formation for both are the same. However, dew is usually formed at night.

Now, let’s discuss the difference between dew and fog in a tabular form:

Distinguish Between Dew and Fog



A condensation that we find on the Earth’s surface. Usually, dewdrops are found on the grass, metals, and cold surfaces.

A fog never settles at a place; basically, it hugs the mountains around itself. It remains in the air. A thick cloud that appears to be at or close to the Earth’s surface.

Calm and peaceful winds lead to the formation of dew.

Light wind speeds to the formation of fog.

Dew is closely linked to frost. When dew freezes further, the formation of frost takes place.

Fog is more often related to the mist. We get the scenic view of fog a.k.a mist in hill stations like Uttarakhand, Himachal Pradesh, etc.

Common in the coldest environment.

Dew formation occurs at night and can be easily viewed by us during mornings.

Fog formation occurs at night and can be easily viewed by us during the mornings.

Important Facts

The occurrence of these tiny droplets on the ground results in difficulty among the players to have a grip on the ball. This difficulty is called the dew factor.

A Dew gauge is a device that measures the amount of dew on the surface.



  • Dewdrops are formed when water vapour condenses and it rests on the cold surfaces, metals, leaves, grasslands, and so on.

  • If we were to distinguish between dew and frost, dew is a tiny droplet that we are already knowledgeable about; however, when these condensed drops freeze further in a cold environment like Ladakh, Yukon, Verkhoyansk, Vostok; these droplets turn to frost.


  • Fog is something that appears to be close to the earth’s surface and we observe this beauty while driving in hill stations. However, the fog never rests on the surface, it remains in the air. 

  • Fog is more often considered the mist that is a thick cloud of tiny water droplets covering the mountains. 

FAQ (Frequently Asked Questions)

1. How is Dew Measured?

Ans: There is a device named ‘Dew gauge’ that measures the amount of dew residing on cold surfaces. 

A dew gauge consists of rectangular slabs. It is a standard device that specifies the requirements of dew gauge wood coated with red oxide paint, which supports the measurements of dew. 

There have been numerous attempts to measure a dew. Among the various instruments, the two are R. Leick’s porous gypsum plates and S. Duvdevani’s dew gauge, comprising a wooden slab coated with paint. To determine the amount of dew on a given surface, Leick’s plates are weighed, whereas Duvdevani’s gauge includes an optical dew scale.

2. Explain the Dew Factor in Cricket.

Ans: Dew Factor is a very essential fact to keep in mind while playing a cricket match in the subcontinent especially in winter. 

The ball is usually made of wood which gets wet in dew and becomes heavy. Thus the speed reduces and makes it difficult for fast bowlers to catch the pace. Spinners fail to get the desired twist because the ball becomes old sooner. However, it is easy to hit old balls and as the pace reduces and the batsman gets privileged time to judge the ball and make scores.

On the dewy grasslands, cricketers avoid bowling at night because, on wet grass, balls run slowly, it becomes hard to have a grip on the ball, and hitting the boundary becomes difficult.