How Does Fog Form?


Up in the sky, clouds form intriguing shapes that block the sun and sometimes bring rain, but when they form near the ground as fog, they can also limit visibility and create hazards. Fog forms in different ways, and it does so because the air has become saturated with moisture.

Radiation Fog

  • The Earth's surface absorbs heat from the sun during the day, and at night it radiates that heat back into space. If there is enough moisture in the air close to the ground, it condenses to form fog as the ground cools. This typically happens when nights are cool, clear and long -- particularly in late autumn.

Advection Fog

  • People living on the West Coast of North America are familiar with the fog banks that blow in from the Pacific Ocean. They form as warm air blows over the colder surface of the ocean, and the change in temperature causes the moisture in the warm air to condense. Advection fog always has a horizontal movement.

Other Types of Fog

  • The fog on mountain slopes is called upslope fog, and it forms as moist air reaches the colder temperatures of the higher altitudes, and the moisture condenses. In temperatures below minus 10 degrees Celsius (14 degrees Fahrenheit), fog consisting entirely of ice crystals can form. On these cold days, evaporation fog can form over warm bodies of water. It occurs because the warm air close to the water condenses when it mixes with the colder ambient air.

Related Searches


  • Photo Credit Igor Kovalenko/iStock/Getty Images
Promoted By Zergnet


You May Also Like

  • How Is Photochemical Smog Formed?

    The brown haze that sometimes blankets urban areas located in mountain basins is known as smog, but it isn't smoke and fog,...

  • What Is Brain Fog?

    Cognitive dysfunction or brain fog is a common condition that affects thousands of people in their work, school and daily activities.

  • What Is Industrial Smog?

    Industrial smog is caused by burning coal and other hydrocarbons. Smog is harmful to humans and can lead to acid rain.

  • How to Stop Eye Glasses From Fogging Up in the Cold

    Glasses can fog up because of an abrupt change in climate, typically from cold to warm and humid, or from sweat beading...

  • The Difference Between Smog & Fog

    When you look up at the sky, you may notice low grayish clouds in the sky. Is it smog or fog? Though...

  • How Does Rust Occur?

    Rust is a common term that is used to describe the oxidization of iron, which occurs when a stable form of iron...

  • How Does Fog Form?

    Fog occurs when the air temperature comes within four degrees Fahrenheit of the dew point, and the dew point is the temperature...

  • Why Is Carbon Important to Living Systems?

    Carbon is important to living systems in that it is found in every form of life, and it can form long chains...

  • How Does a Firefly Produce Light?

    A firefly produces light by taking advantage of a chemical reaction in which luciferin combines with oxygen in the presence of luciferase...

Related Searches

Check It Out

How to Build and Grow a Salad Garden On Your Balcony

Is DIY in your DNA? Become part of our maker community.
Submit Your Work!