Wildscapes Feature

Understanding Cloud and Fog

Why valleys disappear, forest trails turn white and clouds sometimes descend all the way to the ground.

10-minute read 20 July 2026 By Parag Kokane

Low cloud moves through a valley at Varandha Ghat, hiding and revealing cliffs, forest and waterfalls within minutes. Photograph by Parag Kokane.

A cloud is not always above us.
Sometimes, we are walking inside it.

Some landscapes disappear slowly. Others vanish between one bend in the road and the next.

At Varandha Ghat, an open valley may remain visible for a few minutes before a wall of white begins moving through it. Cliffs disappear, waterfalls fade and distant forests lose their shape. A gust of wind clears part of the view, only for the cloud to return moments later.

At Mahabaleshwar or Matheran, a forest trail may continue into white air. At Tamhini or Malshej, the road ahead may suddenly become difficult to see. On cooler mornings around Pune, fields and low-lying areas may lie beneath a quiet layer of fog that disappears after sunrise.

We often use the words mist, fog and cloud for all these scenes. They are closely related, but they do not always form in the same way.

Why does fog appear mostly in the morning in some places, while in the mountains it can arrive at any time of day? Does water stored in wet soil after the rains help create fog? And when cloud surrounds a mountain trail, are we really standing inside a cloud?

The Same Water in the Air

Water is always present in the air as invisible water vapour. It comes from oceans, rivers, lakes, wet soil and plants. When air cools enough, some of this invisible vapour changes into countless tiny droplets.

These droplets are so small that they can remain suspended in the air. Together, they become visible as cloud, fog or mist.

A cloud is a visible collection of tiny water droplets, ice crystals or both. We usually imagine clouds floating high in the sky, but some clouds form much closer to the ground.

Fog is essentially a cloud touching the ground. Meteorologists usually call it fog when visibility falls below one kilometre.

Mist is thinner. Tiny droplets are still present in the air, but we can generally see beyond one kilometre. Distant hills may lose colour and detail, while nearby trees remain visible.

There is no sudden wall where mist becomes fog. The difference is mainly a practical way of describing how far we can see.

Visibility falls across a rain-soaked landscape near Tamhini as tiny droplets surround the ground. Photograph by Parag Kokane.

Cloud, Fog or Mist?

Cloud: tiny water droplets or ice crystals suspended in the air. A low cloud can cross a hill and surround us.

Fog: cloud at ground level that generally reduces visibility to less than one kilometre.

Mist: a thinner layer of droplets through which visibility generally remains greater than one kilometre.

Are We Really Walking Inside a Cloud?

In many mountain situations, the answer is yes.

A cloud does not stop being a cloud simply because it reaches a hill. When a low cloud moves across a ridge, a person watching from the valley sees cloud wrapped around the mountain. A person standing on that ridge experiences the same cloud as fog.

This is common at places such as Varandha, Malshej, Amboli, Mahabaleshwar, Bhimashankar and Tamhini during the rainy season.

Moist winds meet the mountain slopes and are pushed upward. As the air rises, it cools. When it becomes cool enough, water vapour changes into droplets and cloud begins to form.

The shape of the land then controls where the cloud moves. A valley may guide it between two ridges. A gap in the mountains may allow it to pour from one side to the other. A cliff may force the moving air upward, while a sheltered slope may remain clear for a little longer.

This is why the view can change so quickly. The mountain remains where it was. What changes is the layer of droplets moving between us and the landscape.

At Varandha Ghat, cloud occupies the same space as cliffs, forest and waterfalls. From a road or ridge at this height, the cloud is no longer simply part of the sky. Photograph by Parag Kokane.

Why Morning Fog Forms After the Rains

The quiet fog seen around Pune and other inland areas on cooler mornings often forms differently from the moving cloud seen in the mountains.

After the rainy season, moisture remains in the soil, fields, vegetation, lakes, reservoirs and streams. Some of this water slowly enters the air through evaporation. Plants also release moisture through their leaves.

During a clear and calm night, the ground loses heat. The air immediately above it also becomes cooler. If this air cools enough, its water vapour condenses into tiny droplets close to the ground.

This creates the familiar early-morning fog often seen during the cooler months. It is commonly called radiation fog.

The stored moisture in the landscape helps provide water vapour, but the important trigger is cooling. The air must become cool enough for the invisible vapour to turn into visible droplets.

This kind of fog usually forms late at night or before sunrise. Once the Sun warms the ground and the air above it, the droplets begin to evaporate and the fog slowly disappears.

A soft layer of fog lies across the lower landscape when viewed from Malhar Machi. Cooler air close to the ground can turn moisture in the air into visible droplets. Photograph by Parag Kokane.

Not All Fog Forms in the Same Way

Fog may look similar wherever we see it, but it can form through several different processes. The names used by meteorologists describe the conditions that created it.

Five Ways Fog Can Form

Radiation Fog Forms during clear, calm nights when the ground cools the air above it. It is common around fields, lakes and low-lying areas on winter mornings, including parts of Pune and the surrounding countryside.

Valley Fog Forms when cool, heavy air settles in valleys and moisture condenses within it. Valleys around Mahabaleshwar, Koyna, Mulshi and other hilly regions can hold fog below the surrounding ridges.

Hill Fog Forms when moist air is pushed up a slope, cools and turns into cloud. This is the fog commonly experienced at Amboli, Varandha, Malshej, Tamhini, Mahabaleshwar and Bhimashankar during the rainy season.

Advection Fog Forms when moist air moves over a cooler surface and becomes chilled. Under suitable conditions, this can occur along coastal areas, including parts of the Konkan coast.

Steam Fog Forms when cold air moves over warmer water. Moisture rises from the water and quickly condenses, making the surface appear to smoke. This may be seen over rivers, lakes or reservoirs on cold mornings.

Ice Fog Forms in extremely cold air and contains tiny ice crystals rather than only liquid droplets. It may occur in very cold parts of Ladakh and high Himalayan regions during severe winter conditions.

Fog in Valleys and Forests

Valleys are especially good at collecting cool air. Because cool air is heavier than warm air, it can move downhill during the night and settle in lower areas.

If enough moisture is present, fog forms within the valley. From a higher viewpoint, the valley may appear filled with white while the hilltops remain clear.

This can create the impression of islands rising from a white sea. The scene may last only until sunlight reaches the valley floor and begins warming the trapped air.

In mountain forests, fog may arrive for a different reason. Instead of forming quietly overnight, cloud may be carried across the slope by moving air.

A trail at Mahabaleshwar or Amboli may therefore remain clear one moment and disappear the next. The fog is not rising from the forest floor. A low cloud is moving directly through the trees.

Fog surrounds a forest trail at Mahabaleshwar, reducing the landscape to nearby trees, leaves and the path immediately ahead. Photograph by Parag Kokane.

Cloud settles through the valleys of Anuskura Ghat while parts of the surrounding slopes remain visible above it. Photograph by Parag Kokane.

Cloud Around Cold Mountains

The same basic process can be seen in colder mountain regions. Moist air rises along a slope, cools and forms cloud around the forest and higher ridges.

At Gulmarg, cloud may drift across pine-covered mountains while patches of snow remain visible higher on the slope. The presence of snow does not automatically mean that the cloud is ice fog.

Most cloud around such mountains may still contain ordinary liquid droplets, even when the surrounding air feels very cold. Ice fog usually requires much colder conditions close to the ground.

This distinction is useful because appearance alone does not always tell us exactly how a cloud or fog formed. Time of day, temperature, wind, height and local terrain all matter.

Low cloud crosses the forested slopes near Gulmarg, with patches of snow still visible on the mountain. Photograph by Parag Kokane.

Why Mist and Fog Matter to Forests

Mist and fog do more than hide a landscape. They can also add moisture to it.

When cloud moves through a forest, tiny droplets strike leaves, twigs, moss, bark and spider webs. The droplets collect, join together and eventually fall to the ground.

This helps explain why forests around places such as Amboli, Bhimashankar and Mahabaleshwar can remain wet even during a break in the rain. Leaves continue to drip, moss holds water and tree trunks remain dark and damp.

Water reaches the forest not only through rain falling from above, but also through cloud moving directly among the trees.

These moist conditions support ferns, mosses, lichens, fungi, frogs, snails, insects and many other small forms of life. For them, fog is not simply weather. It is part of the habitat.

Fog also changes how we experience a forest. Distant trees disappear, colours become softer and familiar paths lose their sense of distance. Sounds from birds, frogs and unseen animals may seem stronger because the landscape itself is hidden.

Low cloud rests over forested hills during the Devkund trek. Moisture in the air gradually removes colour and detail from the distant ridges. Photograph by Parag Kokane.

Natural History

Do You Know About Indravajra?

On a visit to Matheran, I once saw a remarkable sight. The Sun was behind me, cloud filled the valley ahead and my own shadow appeared on the white surface below.

Around the shadow were faint coloured rings. This phenomenon is often called Indravajra by trekkers and observers in Maharashtra.

The shadow projected onto the cloud is scientifically known as a Brocken spectre. It may appear unusually large because the cloud provides no clear object against which our eyes can judge its distance and size.

The coloured rings around the shadow are called a glory. They form when sunlight is scattered back towards the observer by tiny water droplets within the cloud.

A glory may resemble a small circular rainbow, but it is a different optical effect. It appears around the point directly opposite the Sun, which is also where the observer's shadow falls.

Each observer sees the rings centred around their own shadow. Even when several people are standing together, each person experiences the glory from a slightly different viewpoint.

The best conditions occur when the Sun is behind the observer, cloud or fog lies ahead and there is an open valley or slope onto which the shadow can be projected.

Mountain viewpoints such as Matheran can provide this arrangement when sunlight briefly breaks through above a cloud-filled valley.

The Next Time the Landscape Turns White

The next time fog surrounds a road, trail or valley, pause and look at how it is behaving.

Did it form quietly overnight near the ground? Is it lying below you in a valley? Is cloud moving across a ridge? Is moist air rising along a mountain slope? Or is cold air passing over warmer water?

The white appearance may look similar, but the story behind it can be very different.

On a cool winter morning near Pune, moisture may condense close to fields and lakes after the ground has cooled through the night. At Mahabaleshwar or Amboli, a low cloud may move through the forest during the day. At Varandha or Anuskur, entire valleys may fill and clear repeatedly as the wind changes.

Mist and fog are therefore not simply obstacles that hide a view. They show us how water, air, temperature and land are constantly interacting.

And when sunlight appears behind us while cloud remains ahead, the same white world that hid the mountains may briefly reveal something even more unexpected—our own shadow surrounded by light.

Fog is a cloud we meet at ground level,
but every fog carries the story of how the air cooled.

About Parag Kokane

Parag Kokane is an observer of nature whose work combines field observation, natural history, wildlife photography and writing. Through Wildscapes, he explores the forests, freshwater ecosystems and everyday wildlife of the Western Ghats, sharing stories that encourage readers to look more closely at the natural world around them.