why do we get fog

Fog happens when the air near the ground gets so cool and damp that invisible water vapour turns into tiny floating droplets, making a low cloud you can see.

What fog actually is

Fog is basically a cloud at ground level made of countless tiny liquid water droplets (or sometimes ice crystals) hanging in the air.

It forms when air becomes saturated with moisture, meaning it cannot hold any more water vapour without some of it condensing into droplets.

The basic recipe for fog

For fog to form, two main things usually happen together: the air cools down and the amount of moisture stays high.

Fog commonly appears when the air temperature drops to (or very close to) the “dew point,” the temperature at which water vapour starts to condense into visible droplets.

Different ways we get fog

Scientists describe several common types of fog, which all use that same condensation idea but in different settings.

• Radiation fog: Forms on clear, calm nights when the ground loses heat, cooling the air just above it until water vapour condenses.

• Advection fog: Happens when warm, moist air moves over a colder surface (like cool ocean water or snow) and gets cooled to its dew point.

• Evaporation (steam) fog: Appears when cold air passes over warmer water or wet ground, causing extra moisture to evaporate and then quickly condense into fog.

• Valley or upslope fog: Develops in valleys or along slopes where cooler air pools or is forced to rise and cool, again reaching saturation.

Why some days are foggier than others

Fog is more likely when the air is humid, winds are light, and nights are clear enough for strong cooling at the surface.

Local features like lakes, rivers, and valleys help trap cool, moist air, which is why those places can feel especially fog-prone.

How fog disappears

Weather reports often say fog will “burn off,” but nothing literally burns; the droplets just evaporate.

As the sun warms the ground or drier air moves in, the air temperature rises above the dew point, the droplets evaporate back into invisible water vapour, and visibility improves.

TL;DR: We get fog whenever air near the ground becomes cool and moist enough that water vapour condenses into tiny droplets, turning invisible moisture into a low cloud around us.

Information gathered from public forums or data available on the internet and portrayed here.